Calculus Examples

$\sec^{2} (x)$

Step 1

Consider the limit definition of the derivative.

$f' (x) = lim_{h \to 0} \frac{f (x + h) - f (x)}{h}$

Step 2

Find the components of the definition.

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Step 2.1

Evaluate the function at $x = x + h$ .

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Step 2.1.1

Replace the variable $x$ with $x + h$ in the expression.

$f (x + h) = \sec^{2} (x + h)$

Step 2.1.2

The final answer is $\sec^{2} (x + h)$ .

$\sec^{2} (x + h)$

Step 2.2

Find the components of the definition.

$f (x + h) = \sec^{2} (x + h)$

$f (x) = \sec^{2} (x)$

$f (x + h) = \sec^{2} (x + h)$

$f (x) = \sec^{2} (x)$

Step 3

Plug in the components.

$f' (x) = lim_{h \to 0} \frac{\sec^{2} (x + h) - (\sec^{2} (x))}{h}$

Step 4

Simplify.

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Step 4.1

$f' (x) = lim_{h \to 0} \frac{\frac{1}{\cos^{2} (x + h)} - (\frac{1}{\cos^{2} (x)})}{h}$

Step 4.2

Simplify.

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Step 4.2.1

Simplify the numerator.

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Step 4.2.1.1

Rewrite $1$ as $1^{2}$ .

$f' (x) = lim_{h \to 0} \frac{\frac{1}{\cos^{2} (x + h)} - \frac{1^{2}}{\cos^{2} (x)}}{h}$

Step 4.2.1.2

Rewrite $\frac{1^{2}}{\cos^{2} (x)}$ as ${(\frac{1}{\cos (x)})}^{2}$ .

$f' (x) = lim_{h \to 0} \frac{\frac{1}{\cos^{2} (x + h)} - {(\frac{1}{\cos (x)})}^{2}}{h}$

Step 4.2.1.3

Convert from $\frac{1}{\cos (x)}$ to $\sec (x)$ .

$f' (x) = lim_{h \to 0} \frac{\frac{1}{\cos^{2} (x + h)} - \sec^{2} (x)}{h}$

Step 4.2.1.4

To write $- \sec^{2} (x)$ as a fraction with a common denominator, multiply by $\frac{\cos^{2} (x + h)}{\cos^{2} (x + h)}$ .

$f' (x) = lim_{h \to 0} \frac{\frac{1}{\cos^{2} (x + h)} - \sec^{2} (x) \cdot \frac{\cos^{2} (x + h)}{\cos^{2} (x + h)}}{h}$

Step 4.2.1.5

Combine $- \sec^{2} (x)$ and $\frac{\cos^{2} (x + h)}{\cos^{2} (x + h)}$ .

$f' (x) = lim_{h \to 0} \frac{\frac{1}{\cos^{2} (x + h)} + \frac{- \sec^{2} (x) \cos^{2} (x + h)}{\cos^{2} (x + h)}}{h}$

Step 4.2.1.6

Combine the numerators over the common denominator.

$f' (x) = lim_{h \to 0} \frac{\frac{1 - \sec^{2} (x) \cos^{2} (x + h)}{\cos^{2} (x + h)}}{h}$

Step 4.2.1.7

Rewrite $\frac{1 - \sec^{2} (x) \cos^{2} (x + h)}{\cos^{2} (x + h)}$ in a factored form.

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Step 4.2.1.7.1

Rewrite $1$ as $1^{2}$ .

$f' (x) = lim_{h \to 0} \frac{\frac{1^{2} - \sec^{2} (x) \cos^{2} (x + h)}{\cos^{2} (x + h)}}{h}$

Step 4.2.1.7.2

Rewrite $\sec^{2} (x) \cos^{2} (x + h)$ as ${(\sec (x) \cos (x + h))}^{2}$ .

$f' (x) = lim_{h \to 0} \frac{\frac{1^{2} - {(\sec (x) \cos (x + h))}^{2}}{\cos^{2} (x + h)}}{h}$

Step 4.2.1.7.3

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = 1$ and $b = \sec (x) \cos (x + h)$ .

$f' (x) = lim_{h \to 0} \frac{\frac{(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))}{\cos^{2} (x + h)}}{h}$

Step 4.2.2

Multiply the numerator by the reciprocal of the denominator.

$f' (x) = lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))}{\cos^{2} (x + h)} \cdot \frac{1}{h}$

Step 4.2.3

Combine.

$f' (x) = lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h)) \cdot 1}{\cos^{2} (x + h) h}$

Step 4.2.4

Simplify the expression.

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Step 4.2.4.1

Multiply $1 + \sec (x) \cos (x + h)$ by $1$ .

$f' (x) = lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))}{\cos^{2} (x + h) h}$

Step 4.2.4.2

Reorder factors in $\frac{(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))}{\cos^{2} (x + h) h}$ .

$f' (x) = lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))}{h \cos^{2} (x + h)}$

Step 5

Apply L'Hospital's rule.

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Step 5.1

Evaluate the limit of the numerator and the limit of the denominator.

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Step 5.1.1

Take the limit of the numerator and the limit of the denominator.

$\frac{lim_{h \to 0} (1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2

Evaluate the limit of the numerator.

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Step 5.1.2.1

Split the limit using the Product of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{lim_{h \to 0} 1 + \sec (x) \cos (x + h) \cdot lim_{h \to 0} 1 - \sec (x) \cos (x + h)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.2

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{(lim_{h \to 0} 1 + lim_{h \to 0} \sec (x) \cos (x + h)) \cdot lim_{h \to 0} 1 - \sec (x) \cos (x + h)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.3

Evaluate the limit of $1$ which is constant as $h$ approaches $0$ .

$\frac{(1 + lim_{h \to 0} \sec (x) \cos (x + h)) \cdot lim_{h \to 0} 1 - \sec (x) \cos (x + h)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.4

Move the term $\sec (x)$ outside of the limit because it is constant with respect to $h$ .

$\frac{(1 + \sec (x) lim_{h \to 0} \cos (x + h)) \cdot lim_{h \to 0} 1 - \sec (x) \cos (x + h)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.5

Move the limit inside the trig function because cosine is continuous.

$\frac{(1 + \sec (x) \cos (lim_{h \to 0} x + h)) \cdot lim_{h \to 0} 1 - \sec (x) \cos (x + h)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.6

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{(1 + \sec (x) \cos (lim_{h \to 0} x + lim_{h \to 0} h)) \cdot lim_{h \to 0} 1 - \sec (x) \cos (x + h)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.7

Evaluate the limit of $x$ which is constant as $h$ approaches $0$ .

$\frac{(1 + \sec (x) \cos (x + lim_{h \to 0} h)) \cdot lim_{h \to 0} 1 - \sec (x) \cos (x + h)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.8

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{(1 + \sec (x) \cos (x + lim_{h \to 0} h)) \cdot (lim_{h \to 0} 1 - lim_{h \to 0} \sec (x) \cos (x + h))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.9

Evaluate the limit of $1$ which is constant as $h$ approaches $0$ .

$\frac{(1 + \sec (x) \cos (x + lim_{h \to 0} h)) \cdot (1 - lim_{h \to 0} \sec (x) \cos (x + h))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.10

Move the term $\sec (x)$ outside of the limit because it is constant with respect to $h$ .

$\frac{(1 + \sec (x) \cos (x + lim_{h \to 0} h)) \cdot (1 - \sec (x) lim_{h \to 0} \cos (x + h))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.11

Move the limit inside the trig function because cosine is continuous.

$\frac{(1 + \sec (x) \cos (x + lim_{h \to 0} h)) \cdot (1 - \sec (x) \cos (lim_{h \to 0} x + h))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.12

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{(1 + \sec (x) \cos (x + lim_{h \to 0} h)) \cdot (1 - \sec (x) \cos (lim_{h \to 0} x + lim_{h \to 0} h))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.13

Evaluate the limit of $x$ which is constant as $h$ approaches $0$ .

$\frac{(1 + \sec (x) \cos (x + lim_{h \to 0} h)) \cdot (1 - \sec (x) \cos (x + lim_{h \to 0} h))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.14

Evaluate the limits by plugging in $0$ for all occurrences of $h$ .

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Step 5.1.2.14.1

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{(1 + \sec (x) \cos (x + 0)) \cdot (1 - \sec (x) \cos (x + lim_{h \to 0} h))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.14.2

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{(1 + \sec (x) \cos (x + 0)) \cdot (1 - \sec (x) \cos (x + 0))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15

Simplify the answer.

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Step 5.1.2.15.1

Add $x$ and $0$ .

$\frac{(1 + \sec (x) \cos (x)) \cdot (1 - \sec (x) \cos (x + 0))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.2

Rewrite in terms of sines and cosines, then cancel the common factors.

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Step 5.1.2.15.2.1

Rewrite $\sec (x) \cos (x)$ in terms of sines and cosines.

$\frac{(1 + \frac{1}{\cos (x)} \cos (x)) \cdot (1 - \sec (x) \cos (x + 0))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.2.2

Cancel the common factors.

$\frac{(1 + 1) \cdot (1 - \sec (x) \cos (x + 0))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.3

Add $1$ and $1$ .

$\frac{2 \cdot (1 - \sec (x) \cos (x + 0))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.4

Add $x$ and $0$ .

$\frac{2 \cdot (1 - \sec (x) \cos (x))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.5

Simplify each term.

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Step 5.1.2.15.5.1

Rewrite in terms of sines and cosines, then cancel the common factors.

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Step 5.1.2.15.5.1.1

Add parentheses.

$\frac{2 \cdot (1 - (\sec (x) \cos (x)))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.5.1.2

Rewrite $- \sec (x) \cos (x)$ in terms of sines and cosines.

$\frac{2 \cdot (1 - (\frac{1}{\cos (x)} \cos (x)))}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.5.1.3

Cancel the common factors.

$\frac{2 \cdot (1 - 1 \cdot 1)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.5.2

Multiply $- 1$ by $1$ .

$\frac{2 \cdot (1 - 1)}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.6

Subtract $1$ from $1$ .

$\frac{2 \cdot 0}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.2.15.7

Multiply $2$ by $0$ .

$\frac{0}{lim_{h \to 0} h \cos^{2} (x + h)}$

Step 5.1.3

Evaluate the limit of the denominator.

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Step 5.1.3.1

Split the limit using the Product of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{0}{lim_{h \to 0} h \cdot lim_{h \to 0} \cos^{2} (x + h)}$

Step 5.1.3.2

Move the exponent $2$ from $\cos^{2} (x + h)$ outside the limit using the Limits Power Rule.

$\frac{0}{lim_{h \to 0} h \cdot {(lim_{h \to 0} \cos (x + h))}^{2}}$

Step 5.1.3.3

Move the limit inside the trig function because cosine is continuous.

$\frac{0}{lim_{h \to 0} h \cdot \cos^{2} (lim_{h \to 0} x + h)}$

Step 5.1.3.4

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{0}{lim_{h \to 0} h \cdot \cos^{2} (lim_{h \to 0} x + lim_{h \to 0} h)}$

Step 5.1.3.5

Evaluate the limit of $x$ which is constant as $h$ approaches $0$ .

$\frac{0}{lim_{h \to 0} h \cdot \cos^{2} (x + lim_{h \to 0} h)}$

Step 5.1.3.6

Evaluate the limits by plugging in $0$ for all occurrences of $h$ .

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Step 5.1.3.6.1

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{0}{0 \cdot \cos^{2} (x + lim_{h \to 0} h)}$

Step 5.1.3.6.2

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{0}{0 \cdot \cos^{2} (x + 0)}$

Step 5.1.3.7

Simplify the answer.

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Step 5.1.3.7.1

Add $x$ and $0$ .

$\frac{0}{0 \cdot \cos^{2} (x)}$

Step 5.1.3.7.2

Multiply $0$ by $\cos^{2} (x)$ .

$\frac{0}{0}$

Step 5.1.3.7.3

The expression contains a division by $0$ . The expression is undefined.

Undefined

$\frac{0}{0}$

Step 5.1.3.8

The expression contains a division by $0$ . The expression is undefined.

Undefined

$\frac{0}{0}$

Step 5.1.4

The expression contains a division by $0$ . The expression is undefined.

Undefined

$\frac{0}{0}$

Step 5.2

Since $\frac{0}{0}$ is of indeterminate form, apply L'Hospital's Rule. L'Hospital's Rule states that the limit of a quotient of functions is equal to the limit of the quotient of their derivatives.

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))}{h \cos^{2} (x + h)} = lim_{h \to 0} \frac{\frac{d}{d h} [(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3

Find the derivative of the numerator and denominator.

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Step 5.3.1

Differentiate the numerator and denominator.

$lim_{h \to 0} \frac{\frac{d}{d h} [(1 + \sec (x) \cos (x + h)) (1 - \sec (x) \cos (x + h))]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.2

Differentiate using the Product Rule which states that $\frac{d}{d h} [f (h) g (h)]$ is $f (h) \frac{d}{d h} [g (h)] + g (h) \frac{d}{d h} [f (h)]$ where $f (h) = 1 + \sec (x) \cos (x + h)$ and $g (h) = 1 - \sec (x) \cos (x + h)$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \frac{d}{d h} [1 - \sec (x) \cos (x + h)] + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.3

By the Sum Rule, the derivative of $1 - \sec (x) \cos (x + h)$ with respect to $h$ is $\frac{d}{d h} [1] + \frac{d}{d h} [- \sec (x) \cos (x + h)]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (\frac{d}{d h} [1] + \frac{d}{d h} [- \sec (x) \cos (x + h)]) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.4

Since $1$ is constant with respect to $h$ , the derivative of $1$ with respect to $h$ is $0$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (0 + \frac{d}{d h} [- \sec (x) \cos (x + h)]) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.5

Add $0$ and $\frac{d}{d h} [- \sec (x) \cos (x + h)]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \frac{d}{d h} [- \sec (x) \cos (x + h)] + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.6

Since $- \sec (x)$ is constant with respect to $h$ , the derivative of $- \sec (x) \cos (x + h)$ with respect to $h$ is $- \sec (x) \frac{d}{d h} [\cos (x + h)]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (- \sec (x) \frac{d}{d h} [\cos (x + h)]) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.7

Differentiate using the chain rule, which states that $\frac{d}{d h} [f (g (h))]$ is $f' (g (h)) g' (h)$ where $f (h) = \cos (h)$ and $g (h) = x + h$ .

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Step 5.3.7.1

To apply the Chain Rule, set $u_{1}$ as $x + h$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (- \sec (x) (\frac{d}{d u_{1}} [\cos (u_{1})] \frac{d}{d h} [x + h])) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.7.2

The derivative of $\cos (u_{1})$ with respect to $u_{1}$ is $- \sin (u_{1})$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (- \sec (x) (- \sin (u_{1}) \frac{d}{d h} [x + h])) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.7.3

Replace all occurrences of $u_{1}$ with $x + h$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (- \sec (x) (- \sin (x + h) \frac{d}{d h} [x + h])) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.8

Multiply $- 1$ by $- 1$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (1 \sec (x) (\sin (x + h) \frac{d}{d h} [x + h])) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.9

Multiply $\sec (x)$ by $1$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) (\sec (x) (\sin (x + h) \frac{d}{d h} [x + h])) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.10

By the Sum Rule, the derivative of $x + h$ with respect to $h$ is $\frac{d}{d h} [x] + \frac{d}{d h} [h]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) (\frac{d}{d h} [x] + \frac{d}{d h} [h]) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.11

Since $x$ is constant with respect to $h$ , the derivative of $x$ with respect to $h$ is $0$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) (0 + \frac{d}{d h} [h]) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.12

Add $0$ and $\frac{d}{d h} [h]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) \frac{d}{d h} [h] + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.13

Differentiate using the Power Rule which states that $\frac{d}{d h} [h^{n}]$ is $n h^{n - 1}$ where $n = 1$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) \cdot 1 + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.14

Multiply $1 + \sec (x) \cos (x + h)$ by $1$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [1 + \sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.15

By the Sum Rule, the derivative of $1 + \sec (x) \cos (x + h)$ with respect to $h$ is $\frac{d}{d h} [1] + \frac{d}{d h} [\sec (x) \cos (x + h)]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) (\frac{d}{d h} [1] + \frac{d}{d h} [\sec (x) \cos (x + h)])}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.16

Since $1$ is constant with respect to $h$ , the derivative of $1$ with respect to $h$ is $0$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) (0 + \frac{d}{d h} [\sec (x) \cos (x + h)])}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.17

Add $0$ and $\frac{d}{d h} [\sec (x) \cos (x + h)]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \frac{d}{d h} [\sec (x) \cos (x + h)]}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.18

Since $\sec (x)$ is constant with respect to $h$ , the derivative of $\sec (x) \cos (x + h)$ with respect to $h$ is $\sec (x) \frac{d}{d h} [\cos (x + h)]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) (\sec (x) \frac{d}{d h} [\cos (x + h)])}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.19

Differentiate using the chain rule, which states that $\frac{d}{d h} [f (g (h))]$ is $f' (g (h)) g' (h)$ where $f (h) = \cos (h)$ and $g (h) = x + h$ .

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Step 5.3.19.1

To apply the Chain Rule, set $u_{2}$ as $x + h$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (\frac{d}{d u_{2}} [\cos (u_{2})] \frac{d}{d h} [x + h])}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.19.2

The derivative of $\cos (u_{2})$ with respect to $u_{2}$ is $- \sin (u_{2})$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (- \sin (u_{2}) \frac{d}{d h} [x + h])}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.19.3

Replace all occurrences of $u_{2}$ with $x + h$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (- \sin (x + h) \frac{d}{d h} [x + h])}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.20

By the Sum Rule, the derivative of $x + h$ with respect to $h$ is $\frac{d}{d h} [x] + \frac{d}{d h} [h]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (- \sin (x + h) (\frac{d}{d h} [x] + \frac{d}{d h} [h]))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.21

Since $x$ is constant with respect to $h$ , the derivative of $x$ with respect to $h$ is $0$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (- \sin (x + h) (0 + \frac{d}{d h} [h]))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.22

Add $0$ and $\frac{d}{d h} [h]$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (- \sin (x + h) \frac{d}{d h} [h])}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.23

Differentiate using the Power Rule which states that $\frac{d}{d h} [h^{n}]$ is $n h^{n - 1}$ where $n = 1$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (- \sin (x + h) \cdot 1)}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.24

Multiply $- 1$ by $1$ .

$lim_{h \to 0} \frac{(1 + \sec (x) \cos (x + h)) \sec (x) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25

Simplify.

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Step 5.3.25.1

Apply the distributive property.

$lim_{h \to 0} \frac{(1 \sec (x) + \sec (x) \cos (x + h) \sec (x)) \sin (x + h) + (1 - \sec (x) \cos (x + h)) \sec (x) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.2

Apply the distributive property.

$lim_{h \to 0} \frac{(1 \sec (x) + \sec (x) \cos (x + h) \sec (x)) \sin (x + h) + (1 \sec (x) - \sec (x) \cos (x + h) \sec (x)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3

Combine terms.

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Step 5.3.25.3.1

Multiply $\sec (x)$ by $1$ .

$lim_{h \to 0} \frac{(\sec (x) + \sec (x) \cos (x + h) \sec (x)) \sin (x + h) + (1 \sec (x) - \sec (x) \cos (x + h) \sec (x)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.2

Raise $\sec (x)$ to the power of $1$ .

$lim_{h \to 0} \frac{(\sec (x) + \sec^{1} (x) \sec (x) \cos (x + h)) \sin (x + h) + (1 \sec (x) - \sec (x) \cos (x + h) \sec (x)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.3

Raise $\sec (x)$ to the power of $1$ .

$lim_{h \to 0} \frac{(\sec (x) + \sec^{1} (x) \sec^{1} (x) \cos (x + h)) \sin (x + h) + (1 \sec (x) - \sec (x) \cos (x + h) \sec (x)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.4

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$lim_{h \to 0} \frac{(\sec (x) + {\sec (x)}^{1 + 1} \cos (x + h)) \sin (x + h) + (1 \sec (x) - \sec (x) \cos (x + h) \sec (x)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.5

Add $1$ and $1$ .

$lim_{h \to 0} \frac{(\sec (x) + \sec^{2} (x) \cos (x + h)) \sin (x + h) + (1 \sec (x) - \sec (x) \cos (x + h) \sec (x)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.6

Multiply $\sec (x)$ by $1$ .

$lim_{h \to 0} \frac{(\sec (x) + \sec^{2} (x) \cos (x + h)) \sin (x + h) + (\sec (x) - \sec (x) \cos (x + h) \sec (x)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.7

Raise $\sec (x)$ to the power of $1$ .

$lim_{h \to 0} \frac{(\sec (x) + \sec^{2} (x) \cos (x + h)) \sin (x + h) + (\sec (x) - (\sec^{1} (x) \sec (x)) \cos (x + h)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.8

Raise $\sec (x)$ to the power of $1$ .

$lim_{h \to 0} \frac{(\sec (x) + \sec^{2} (x) \cos (x + h)) \sin (x + h) + (\sec (x) - (\sec^{1} (x) \sec^{1} (x)) \cos (x + h)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.9

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$lim_{h \to 0} \frac{(\sec (x) + \sec^{2} (x) \cos (x + h)) \sin (x + h) + (\sec (x) - {\sec (x)}^{1 + 1} \cos (x + h)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.3.10

Add $1$ and $1$ .

$lim_{h \to 0} \frac{(\sec (x) + \sec^{2} (x) \cos (x + h)) \sin (x + h) + (\sec (x) - \sec^{2} (x) \cos (x + h)) (- \sin (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.4

Reorder terms.

$lim_{h \to 0} \frac{\sin (x + h) (\sec (x) + \sec^{2} (x) \cos (x + h)) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5

Simplify each term.

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Step 5.3.25.5.1

Simplify each term.

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Step 5.3.25.5.1.1

Rewrite $\sec (x)$ in terms of sines and cosines.

$lim_{h \to 0} \frac{\sin (x + h) (\frac{1}{\cos (x)} + \sec^{2} (x) \cos (x + h)) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.1.2

Rewrite $\sec (x)$ in terms of sines and cosines.

$lim_{h \to 0} \frac{\sin (x + h) (\frac{1}{\cos (x)} + {(\frac{1}{\cos (x)})}^{2} \cos (x + h)) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.1.3

Apply the product rule to $\frac{1}{\cos (x)}$ .

$lim_{h \to 0} \frac{\sin (x + h) (\frac{1}{\cos (x)} + \frac{1^{2}}{\cos^{2} (x)} \cos (x + h)) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.1.4

One to any power is one.

$lim_{h \to 0} \frac{\sin (x + h) (\frac{1}{\cos (x)} + \frac{1}{\cos^{2} (x)} \cos (x + h)) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.1.5

Combine $\frac{1}{\cos^{2} (x)}$ and $\cos (x + h)$ .

$lim_{h \to 0} \frac{\sin (x + h) (\frac{1}{\cos (x)} + \frac{\cos (x + h)}{\cos^{2} (x)}) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.2

To write $\frac{1}{\cos (x)}$ as a fraction with a common denominator, multiply by $\frac{\cos (x)}{\cos (x)}$ .

$lim_{h \to 0} \frac{\sin (x + h) (\frac{1}{\cos (x)} \cdot \frac{\cos (x)}{\cos (x)} + \frac{\cos (x + h)}{\cos^{2} (x)}) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.3

Write each expression with a common denominator of $\cos^{2} (x)$ , by multiplying each by an appropriate factor of $1$ .

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Step 5.3.25.5.3.1

Multiply $\frac{1}{\cos (x)}$ by $\frac{\cos (x)}{\cos (x)}$ .

$lim_{h \to 0} \frac{\sin (x + h) (\frac{\cos (x)}{\cos (x) \cos (x)} + \frac{\cos (x + h)}{\cos^{2} (x)}) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.3.2

Multiply $\cos (x) \cos (x)$ .

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Step 5.3.25.5.3.2.1

Raise $\cos (x)$ to the power of $1$ .

$lim_{h \to 0} \frac{\sin (x + h) (\frac{\cos (x)}{\cos^{1} (x) \cos (x)} + \frac{\cos (x + h)}{\cos^{2} (x)}) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.3.2.2

Raise $\cos (x)$ to the power of $1$ .

$lim_{h \to 0} \frac{\sin (x + h) (\frac{\cos (x)}{\cos^{1} (x) \cos^{1} (x)} + \frac{\cos (x + h)}{\cos^{2} (x)}) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.3.2.3

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$lim_{h \to 0} \frac{\sin (x + h) (\frac{\cos (x)}{{\cos (x)}^{1 + 1}} + \frac{\cos (x + h)}{\cos^{2} (x)}) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.3.2.4

Add $1$ and $1$ .

$lim_{h \to 0} \frac{\sin (x + h) (\frac{\cos (x)}{\cos^{2} (x)} + \frac{\cos (x + h)}{\cos^{2} (x)}) - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.4

Combine the numerators over the common denominator.

$lim_{h \to 0} \frac{\sin (x + h) \frac{\cos (x) + \cos (x + h)}{\cos^{2} (x)} - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.5

Combine $\sin (x + h)$ and $\frac{\cos (x) + \cos (x + h)}{\cos^{2} (x)}$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\sec (x) - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.6

Simplify each term.

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Step 5.3.25.5.6.1

Rewrite $\sec (x)$ in terms of sines and cosines.

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{1}{\cos (x)} - \sec^{2} (x) \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.6.2

Rewrite $\sec (x)$ in terms of sines and cosines.

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{1}{\cos (x)} - {(\frac{1}{\cos (x)})}^{2} \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.6.3

Apply the product rule to $\frac{1}{\cos (x)}$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{1}{\cos (x)} - \frac{1^{2}}{\cos^{2} (x)} \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.6.4

One to any power is one.

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{1}{\cos (x)} - \frac{1}{\cos^{2} (x)} \cos (x + h))}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.6.5

Combine $\cos (x + h)$ and $\frac{1}{\cos^{2} (x)}$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{1}{\cos (x)} - \frac{\cos (x + h)}{\cos^{2} (x)})}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.7

To write $\frac{1}{\cos (x)}$ as a fraction with a common denominator, multiply by $\frac{\cos (x)}{\cos (x)}$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{1}{\cos (x)} \cdot \frac{\cos (x)}{\cos (x)} - \frac{\cos (x + h)}{\cos^{2} (x)})}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.8

Write each expression with a common denominator of $\cos^{2} (x)$ , by multiplying each by an appropriate factor of $1$ .

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Step 5.3.25.5.8.1

Multiply $\frac{1}{\cos (x)}$ by $\frac{\cos (x)}{\cos (x)}$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{\cos (x)}{\cos (x) \cos (x)} - \frac{\cos (x + h)}{\cos^{2} (x)})}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.8.2

Multiply $\cos (x) \cos (x)$ .

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Step 5.3.25.5.8.2.1

Raise $\cos (x)$ to the power of $1$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{\cos (x)}{\cos^{1} (x) \cos (x)} - \frac{\cos (x + h)}{\cos^{2} (x)})}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.8.2.2

Raise $\cos (x)$ to the power of $1$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{\cos (x)}{\cos^{1} (x) \cos^{1} (x)} - \frac{\cos (x + h)}{\cos^{2} (x)})}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.8.2.3

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{\cos (x)}{{\cos (x)}^{1 + 1}} - \frac{\cos (x + h)}{\cos^{2} (x)})}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.8.2.4

Add $1$ and $1$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) (\frac{\cos (x)}{\cos^{2} (x)} - \frac{\cos (x + h)}{\cos^{2} (x)})}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.9

Combine the numerators over the common denominator.

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \sin (x + h) \frac{\cos (x) - \cos (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.5.10

Combine $\frac{\cos (x) - \cos (x + h)}{\cos^{2} (x)}$ and $\sin (x + h)$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h))}{\cos^{2} (x)} - \frac{(\cos (x) - \cos (x + h)) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.6

Combine the numerators over the common denominator.

$lim_{h \to 0} \frac{\frac{\sin (x + h) (\cos (x) + \cos (x + h)) - (\cos (x) - \cos (x + h)) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.7

Simplify each term.

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Step 5.3.25.7.1

Apply the distributive property.

$lim_{h \to 0} \frac{\frac{\sin (x + h) \cos (x) + \sin (x + h) \cos (x + h) - (\cos (x) - \cos (x + h)) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.7.2

Apply the distributive property.

$lim_{h \to 0} \frac{\frac{\sin (x + h) \cos (x) + \sin (x + h) \cos (x + h) + (- \cos (x) - - \cos (x + h)) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.7.3

Multiply $- - \cos (x + h)$ .

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Step 5.3.25.7.3.1

Multiply $- 1$ by $- 1$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) \cos (x) + \sin (x + h) \cos (x + h) + (- \cos (x) + 1 \cos (x + h)) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.7.3.2

Multiply $\cos (x + h)$ by $1$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) \cos (x) + \sin (x + h) \cos (x + h) + (- \cos (x) + \cos (x + h)) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.7.4

Apply the distributive property.

$lim_{h \to 0} \frac{\frac{\sin (x + h) \cos (x) + \sin (x + h) \cos (x + h) - \cos (x) \sin (x + h) + \cos (x + h) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.8

Combine the opposite terms in $\sin (x + h) \cos (x) + \sin (x + h) \cos (x + h) - \cos (x) \sin (x + h) + \cos (x + h) \sin (x + h)$ .

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Step 5.3.25.8.1

Reorder the factors in the terms $\sin (x + h) \cos (x)$ and $- \cos (x) \sin (x + h)$ .

$lim_{h \to 0} \frac{\frac{\cos (x) \sin (x + h) + \sin (x + h) \cos (x + h) - \cos (x) \sin (x + h) + \cos (x + h) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.8.2

Subtract $\cos (x) \sin (x + h)$ from $\cos (x) \sin (x + h)$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) \cos (x + h) + 0 + \cos (x + h) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.8.3

Add $\sin (x + h) \cos (x + h)$ and $0$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) \cos (x + h) + \cos (x + h) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.9

Reorder the factors of $\sin (x + h) \cos (x + h)$ .

$lim_{h \to 0} \frac{\frac{\cos (x + h) \sin (x + h) + \cos (x + h) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.10

Add $\cos (x + h) \sin (x + h)$ and $\cos (x + h) \sin (x + h)$ .

$lim_{h \to 0} \frac{\frac{2 \cos (x + h) \sin (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.11

Reorder $2 \cos (x + h)$ and $\sin (x + h)$ .

$lim_{h \to 0} \frac{\frac{\sin (x + h) (2 \cos (x + h))}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.12

Reorder $\sin (x + h)$ and $2$ .

$lim_{h \to 0} \frac{\frac{2 \cdot \sin (x + h) \cos (x + h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.13

Apply the sine double-angle identity.

$lim_{h \to 0} \frac{\frac{\sin (2 (x + h))}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.25.14

Apply the distributive property.

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{\frac{d}{d h} [h \cos^{2} (x + h)]}$

Step 5.3.26

Differentiate using the Product Rule which states that $\frac{d}{d h} [f (h) g (h)]$ is $f (h) \frac{d}{d h} [g (h)] + g (h) \frac{d}{d h} [f (h)]$ where $f (h) = h$ and $g (h) = \cos^{2} (x + h)$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h \frac{d}{d h} [\cos^{2} (x + h)] + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.27

Differentiate using the chain rule, which states that $\frac{d}{d h} [f (g (h))]$ is $f' (g (h)) g' (h)$ where $f (h) = h^{2}$ and $g (h) = \cos (x + h)$ .

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Step 5.3.27.1

To apply the Chain Rule, set $u_{1}$ as $\cos (x + h)$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (\frac{d}{d u_{1}} [{u_{1}}^{2}] \frac{d}{d h} [\cos (x + h)]) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.27.2

Differentiate using the Power Rule which states that $\frac{d}{d u_{1}} [{u_{1}}^{n}]$ is $n {u_{1}}^{n - 1}$ where $n = 2$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (2 u_{1} \frac{d}{d h} [\cos (x + h)]) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.27.3

Replace all occurrences of $u_{1}$ with $\cos (x + h)$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (2 \cos (x + h) \frac{d}{d h} [\cos (x + h)]) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.28

Differentiate using the chain rule, which states that $\frac{d}{d h} [f (g (h))]$ is $f' (g (h)) g' (h)$ where $f (h) = \cos (h)$ and $g (h) = x + h$ .

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Step 5.3.28.1

To apply the Chain Rule, set $u_{2}$ as $x + h$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (2 \cos (x + h) (\frac{d}{d u_{2}} [\cos (u_{2})] \frac{d}{d h} [x + h])) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.28.2

The derivative of $\cos (u_{2})$ with respect to $u_{2}$ is $- \sin (u_{2})$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (2 \cos (x + h) (- \sin (u_{2}) \frac{d}{d h} [x + h])) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.28.3

Replace all occurrences of $u_{2}$ with $x + h$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (2 \cos (x + h) (- \sin (x + h) \frac{d}{d h} [x + h])) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.29

Multiply $- 1$ by $2$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (- 2 \cos (x + h) (\sin (x + h) \frac{d}{d h} [x + h])) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.30

By the Sum Rule, the derivative of $x + h$ with respect to $h$ is $\frac{d}{d h} [x] + \frac{d}{d h} [h]$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (- 2 \cos (x + h) \sin (x + h) (\frac{d}{d h} [x] + \frac{d}{d h} [h])) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.31

Since $x$ is constant with respect to $h$ , the derivative of $x$ with respect to $h$ is $0$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (- 2 \cos (x + h) \sin (x + h) (0 + \frac{d}{d h} [h])) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.32

Add $0$ and $\frac{d}{d h} [h]$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (- 2 \cos (x + h) \sin (x + h) \frac{d}{d h} [h]) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.33

Differentiate using the Power Rule which states that $\frac{d}{d h} [h^{n}]$ is $n h^{n - 1}$ where $n = 1$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (- 2 \cos (x + h) \sin (x + h) \cdot 1) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.34

Multiply $- 2$ by $1$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (- 2 \cos (x + h) \sin (x + h)) + \cos^{2} (x + h) \frac{d}{d h} [h]}$

Step 5.3.35

Differentiate using the Power Rule which states that $\frac{d}{d h} [h^{n}]$ is $n h^{n - 1}$ where $n = 1$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (- 2 \cos (x + h) \sin (x + h)) + \cos^{2} (x + h) \cdot 1}$

Step 5.3.36

Multiply $\cos^{2} (x + h)$ by $1$ .

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{h (- 2 \cos (x + h) \sin (x + h)) + \cos^{2} (x + h)}$

Step 5.3.37

Reorder terms.

$lim_{h \to 0} \frac{\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}}{- 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$

Step 5.4

Multiply the numerator by the reciprocal of the denominator.

$lim_{h \to 0} \frac{\sin (2 x + 2 h)}{\cos^{2} (x)} \cdot \frac{1}{- 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$

Step 5.5

Multiply $\frac{\sin (2 x + 2 h)}{\cos^{2} (x)}$ by $\frac{1}{- 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$ .

$lim_{h \to 0} \frac{\sin (2 x + 2 h)}{\cos^{2} (x) (- 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h))}$

Step 6

Evaluate the limit.

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Step 6.1

Move the term $\frac{1}{\cos^{2} (x)}$ outside of the limit because it is constant with respect to $h$ .

$\frac{1}{\cos^{2} (x)} lim_{h \to 0} \frac{\sin (2 x + 2 h)}{- 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$

Step 6.2

Split the limit using the Limits Quotient Rule on the limit as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{lim_{h \to 0} \sin (2 x + 2 h)}{lim_{h \to 0} - 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$

Step 6.3

Move the limit inside the trig function because sine is continuous.

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (lim_{h \to 0} 2 x + 2 h)}{lim_{h \to 0} - 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$

Step 6.4

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (lim_{h \to 0} 2 x + lim_{h \to 0} 2 h)}{lim_{h \to 0} - 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$

Step 6.5

Evaluate the limit of $2 x$ which is constant as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + lim_{h \to 0} 2 h)}{lim_{h \to 0} - 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$

Step 6.6

Move the term $2$ outside of the limit because it is constant with respect to $h$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{lim_{h \to 0} - 2 h \cos (x + h) \sin (x + h) + \cos^{2} (x + h)}$

Step 6.7

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- lim_{h \to 0} 2 h \cos (x + h) \sin (x + h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.8

Move the term $2$ outside of the limit because it is constant with respect to $h$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cos (x + h) \sin (x + h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.9

Split the limit using the Product of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot lim_{h \to 0} \cos (x + h) \cdot lim_{h \to 0} \sin (x + h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.10

Move the limit inside the trig function because cosine is continuous.

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (lim_{h \to 0} x + h) \cdot lim_{h \to 0} \sin (x + h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.11

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (lim_{h \to 0} x + lim_{h \to 0} h) \cdot lim_{h \to 0} \sin (x + h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.12

Evaluate the limit of $x$ which is constant as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot lim_{h \to 0} \sin (x + h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.13

Move the limit inside the trig function because sine is continuous.

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (lim_{h \to 0} x + h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.14

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (lim_{h \to 0} x + lim_{h \to 0} h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.15

Evaluate the limit of $x$ which is constant as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (x + lim_{h \to 0} h) + lim_{h \to 0} \cos^{2} (x + h)}$

Step 6.16

Move the exponent $2$ from $\cos^{2} (x + h)$ outside the limit using the Limits Power Rule.

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (x + lim_{h \to 0} h) + {(lim_{h \to 0} \cos (x + h))}^{2}}$

Step 6.17

Move the limit inside the trig function because cosine is continuous.

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (x + lim_{h \to 0} h) + \cos^{2} (lim_{h \to 0} x + h)}$

Step 6.18

Split the limit using the Sum of Limits Rule on the limit as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (x + lim_{h \to 0} h) + \cos^{2} (lim_{h \to 0} x + lim_{h \to 0} h)}$

Step 6.19

Evaluate the limit of $x$ which is constant as $h$ approaches $0$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 lim_{h \to 0} h)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (x + lim_{h \to 0} h) + \cos^{2} (x + lim_{h \to 0} h)}$

Step 7

Evaluate the limits by plugging in $0$ for all occurrences of $h$ .

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Step 7.1

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 \cdot 0)}{- 2 lim_{h \to 0} h \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (x + lim_{h \to 0} h) + \cos^{2} (x + lim_{h \to 0} h)}$

Step 7.2

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 \cdot 0)}{- 2 \cdot 0 \cdot \cos (x + lim_{h \to 0} h) \cdot \sin (x + lim_{h \to 0} h) + \cos^{2} (x + lim_{h \to 0} h)}$

Step 7.3

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 \cdot 0)}{- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + lim_{h \to 0} h) + \cos^{2} (x + lim_{h \to 0} h)}$

Step 7.4

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 \cdot 0)}{- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0) + \cos^{2} (x + lim_{h \to 0} h)}$

Step 7.5

Evaluate the limit of $h$ by plugging in $0$ for $h$ .

$\frac{1}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 \cdot 0)}{- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0) + \cos^{2} (x + 0)}$

Step 8

Simplify the answer.

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Step 8.1

Rewrite $1$ as $1^{2}$ .

$\frac{1^{2}}{\cos^{2} (x)} \cdot \frac{\sin (2 x + 2 \cdot 0)}{- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0) + \cos^{2} (x + 0)}$

Step 8.2

Rewrite $\frac{1^{2}}{\cos^{2} (x)}$ as ${(\frac{1}{\cos (x)})}^{2}$ .

${(\frac{1}{\cos (x)})}^{2} \frac{\sin (2 x + 2 \cdot 0)}{- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0) + \cos^{2} (x + 0)}$

Step 8.3

Convert from $\frac{1}{\cos (x)}$ to $\sec (x)$ .

$\sec^{2} (x) \frac{\sin (2 x + 2 \cdot 0)}{- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0) + \cos^{2} (x + 0)}$

Step 8.4

Simplify the numerator.

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Step 8.4.1

Multiply $2$ by $0$ .

$\sec^{2} (x) \frac{\sin (2 x + 0)}{- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0) + \cos^{2} (x + 0)}$

Step 8.4.2

Add $2 x$ and $0$ .

$\sec^{2} (x) \frac{\sin (2 x)}{- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0) + \cos^{2} (x + 0)}$

Step 8.5

Simplify the denominator.

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Step 8.5.1

Factor $\cos (x + 0)$ out of $- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0) + \cos^{2} (x + 0)$ .

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Step 8.5.1.1

Factor $\cos (x + 0)$ out of $- 2 \cdot 0 \cdot \cos (x + 0) \cdot \sin (x + 0)$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x + 0) (- 2 \cdot 0 \cdot \sin (x + 0)) + \cos^{2} (x + 0)}$

Step 8.5.1.2

Factor $\cos (x + 0)$ out of $\cos^{2} (x + 0)$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x + 0) (- 2 \cdot 0 \cdot \sin (x + 0)) + \cos (x + 0) \cos (x + 0)}$

Step 8.5.1.3

Factor $\cos (x + 0)$ out of $\cos (x + 0) (- 2 \cdot 0 \cdot \sin (x + 0)) + \cos (x + 0) \cos (x + 0)$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x + 0) (- 2 \cdot 0 \cdot \sin (x + 0) + \cos (x + 0))}$

Step 8.5.2

Multiply $- 2$ by $0$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x + 0) (0 \cdot \sin (x + 0) + \cos (x + 0))}$

Step 8.5.3

Add $x$ and $0$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x + 0) (0 \cdot \sin (x) + \cos (x + 0))}$

Step 8.5.4

Multiply $0$ by $\sin (x)$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x + 0) (0 + \cos (x + 0))}$

Step 8.5.5

Add $x$ and $0$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x + 0) (0 + \cos (x))}$

Step 8.5.6

Add $0$ and $\cos (x)$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x + 0) \cos (x)}$

Step 8.5.7

Add $x$ and $0$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos (x) \cos (x)}$

Step 8.6

Simplify the denominator.

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Step 8.6.1

Raise $\cos (x)$ to the power of $1$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos^{1} (x) \cos (x)}$

Step 8.6.2

Raise $\cos (x)$ to the power of $1$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos^{1} (x) \cos^{1} (x)}$

Step 8.6.3

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\sec^{2} (x) \frac{\sin (2 x)}{{\cos (x)}^{1 + 1}}$

Step 8.6.4

Add $1$ and $1$ .

$\sec^{2} (x) \frac{\sin (2 x)}{\cos^{2} (x)}$

Step 8.7

Apply the sine double-angle identity.

$\sec^{2} (x) \frac{2 \sin (x) \cos (x)}{\cos^{2} (x)}$

Step 8.8

Cancel the common factor of $\cos (x)$ and $\cos^{2} (x)$ .

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Step 8.8.1

Factor $\cos (x)$ out of $2 \sin (x) \cos (x)$ .

$\sec^{2} (x) \frac{\cos (x) (2 \sin (x))}{\cos^{2} (x)}$

Step 8.8.2

Cancel the common factors.

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Step 8.8.2.1

Factor $\cos (x)$ out of $\cos^{2} (x)$ .

$\sec^{2} (x) \frac{\cos (x) (2 \sin (x))}{\cos (x) \cos (x)}$

Step 8.8.2.2

Cancel the common factor.

$\sec^{2} (x) \frac{\cos (x) (2 \sin (x))}{\cos (x) \cos (x)}$

Step 8.8.2.3

Rewrite the expression.

$\sec^{2} (x) \frac{2 \sin (x)}{\cos (x)}$

Step 8.9

Separate fractions.

$\sec^{2} (x) (\frac{2}{1} \cdot \frac{\sin (x)}{\cos (x)})$

Step 8.10

Convert from $\frac{\sin (x)}{\cos (x)}$ to $\tan (x)$ .

$\sec^{2} (x) (\frac{2}{1} \tan (x))$

Step 8.11

Rewrite using the commutative property of multiplication.

$\frac{2}{1} \sec^{2} (x) \tan (x)$

Step 8.12

Divide $2$ by $1$ .

$2 \sec^{2} (x) \tan (x)$

Step 9