Calculus Examples

$lim_{x \to 0} \frac{\sin^{3} (5 x)}{x^{3}}$

Step 1

Apply L'Hospital's rule.

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Step 1.1

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

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Step 1.1.1

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

$\frac{lim_{x \to 0} \sin^{3} (5 x)}{lim_{x \to 0} x^{3}}$

Step 1.1.2

Evaluate the limit of the numerator.

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Step 1.1.2.1

Evaluate the limit.

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Step 1.1.2.1.1

Move the exponent $3$ from $\sin^{3} (5 x)$ outside the limit using the Limits Power Rule.

$\frac{{(lim_{x \to 0} \sin (5 x))}^{3}}{lim_{x \to 0} x^{3}}$

Step 1.1.2.1.2

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

$\frac{\sin^{3} (lim_{x \to 0} 5 x)}{lim_{x \to 0} x^{3}}$

Step 1.1.2.1.3

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$\frac{\sin^{3} (5 lim_{x \to 0} x)}{lim_{x \to 0} x^{3}}$

Step 1.1.2.2

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

$\frac{\sin^{3} (5 \cdot 0)}{lim_{x \to 0} x^{3}}$

Step 1.1.2.3

Simplify the answer.

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Step 1.1.2.3.1

Multiply $5$ by $0$ .

$\frac{\sin^{3} (0)}{lim_{x \to 0} x^{3}}$

Step 1.1.2.3.2

The exact value of $\sin (0)$ is $0$ .

$\frac{0^{3}}{lim_{x \to 0} x^{3}}$

Step 1.1.2.3.3

Raising $0$ to any positive power yields $0$ .

$\frac{0}{lim_{x \to 0} x^{3}}$

Step 1.1.3

Evaluate the limit of the denominator.

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Step 1.1.3.1

Move the exponent $3$ from $x^{3}$ outside the limit using the Limits Power Rule.

$\frac{0}{{(lim_{x \to 0} x)}^{3}}$

Step 1.1.3.2

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

$\frac{0}{0^{3}}$

Step 1.1.3.3

Raising $0$ to any positive power yields $0$ .

$\frac{0}{0}$

Step 1.1.3.4

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

Undefined

$\frac{0}{0}$

Step 1.1.4

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

Undefined

$\frac{0}{0}$

Step 1.2

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.

$lim_{x \to 0} \frac{\sin^{3} (5 x)}{x^{3}} = lim_{x \to 0} \frac{\frac{d}{d x} [\sin^{3} (5 x)]}{\frac{d}{d x} [x^{3}]}$

Step 1.3

Find the derivative of the numerator and denominator.

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Step 1.3.1

Differentiate the numerator and denominator.

$lim_{x \to 0} \frac{\frac{d}{d x} [\sin^{3} (5 x)]}{\frac{d}{d x} [x^{3}]}$

Step 1.3.2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{3}$ and $g (x) = \sin (5 x)$ .

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Step 1.3.2.1

To apply the Chain Rule, set $u_{1}$ as $\sin (5 x)$ .

$lim_{x \to 0} \frac{\frac{d}{d u_{1}} [{u_{1}}^{3}] \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x^{3}]}$

Step 1.3.2.2

Differentiate using the Power Rule which states that $\frac{d}{d u_{1}} [{u_{1}}^{n}]$ is $n {u_{1}}^{n - 1}$ where $n = 3$ .

$lim_{x \to 0} \frac{3 {u_{1}}^{2} \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x^{3}]}$

Step 1.3.2.3

Replace all occurrences of $u_{1}$ with $\sin (5 x)$ .

$lim_{x \to 0} \frac{3 \sin^{2} (5 x) \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x^{3}]}$

Step 1.3.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \sin (x)$ and $g (x) = 5 x$ .

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Step 1.3.3.1

To apply the Chain Rule, set $u_{2}$ as $5 x$ .

$lim_{x \to 0} \frac{3 \sin^{2} (5 x) (\frac{d}{d u_{2}} [\sin (u_{2})] \frac{d}{d x} [5 x])}{\frac{d}{d x} [x^{3}]}$

Step 1.3.3.2

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

$lim_{x \to 0} \frac{3 \sin^{2} (5 x) (\cos (u_{2}) \frac{d}{d x} [5 x])}{\frac{d}{d x} [x^{3}]}$

Step 1.3.3.3

Replace all occurrences of $u_{2}$ with $5 x$ .

$lim_{x \to 0} \frac{3 \sin^{2} (5 x) (\cos (5 x) \frac{d}{d x} [5 x])}{\frac{d}{d x} [x^{3}]}$

Step 1.3.4

Since $5$ is constant with respect to $x$ , the derivative of $5 x$ with respect to $x$ is $5 \frac{d}{d x} [x]$ .

$lim_{x \to 0} \frac{3 \sin^{2} (5 x) \cos (5 x) (5 \frac{d}{d x} [x])}{\frac{d}{d x} [x^{3}]}$

Step 1.3.5

Multiply $5$ by $3$ .

$lim_{x \to 0} \frac{15 \sin^{2} (5 x) \cos (5 x) \frac{d}{d x} [x]}{\frac{d}{d x} [x^{3}]}$

Step 1.3.6

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

$lim_{x \to 0} \frac{15 \sin^{2} (5 x) \cos (5 x) \cdot 1}{\frac{d}{d x} [x^{3}]}$

Step 1.3.7

Multiply $15$ by $1$ .

$lim_{x \to 0} \frac{15 \sin^{2} (5 x) \cos (5 x)}{\frac{d}{d x} [x^{3}]}$

Step 1.3.8

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 3$ .

$lim_{x \to 0} \frac{15 \sin^{2} (5 x) \cos (5 x)}{3 x^{2}}$

Step 1.4

Cancel the common factor of $15$ and $3$ .

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Step 1.4.1

Factor $3$ out of $15 \sin^{2} (5 x) \cos (5 x)$ .

$lim_{x \to 0} \frac{3 (5 \sin^{2} (5 x) \cos (5 x))}{3 x^{2}}$

Step 1.4.2

Cancel the common factors.

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Step 1.4.2.1

Factor $3$ out of $3 x^{2}$ .

$lim_{x \to 0} \frac{3 (5 \sin^{2} (5 x) \cos (5 x))}{3 (x^{2})}$

Step 1.4.2.2

Cancel the common factor.

$lim_{x \to 0} \frac{3 (5 \sin^{2} (5 x) \cos (5 x))}{3 x^{2}}$

Step 1.4.2.3

Rewrite the expression.

$lim_{x \to 0} \frac{5 \sin^{2} (5 x) \cos (5 x)}{x^{2}}$

Step 2

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 lim_{x \to 0} \frac{\sin^{2} (5 x) \cos (5 x)}{x^{2}}$

Step 3

Apply L'Hospital's rule.

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Step 3.1

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

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Step 3.1.1

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

$5 \frac{lim_{x \to 0} \sin^{2} (5 x) \cos (5 x)}{lim_{x \to 0} x^{2}}$

Step 3.1.2

Evaluate the limit of the numerator.

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Step 3.1.2.1

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

$5 \frac{lim_{x \to 0} \sin^{2} (5 x) \cdot lim_{x \to 0} \cos (5 x)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.2

Move the exponent $2$ from $\sin^{2} (5 x)$ outside the limit using the Limits Power Rule.

$5 \frac{{(lim_{x \to 0} \sin (5 x))}^{2} \cdot lim_{x \to 0} \cos (5 x)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.3

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

$5 \frac{\sin^{2} (lim_{x \to 0} 5 x) \cdot lim_{x \to 0} \cos (5 x)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.4

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 \frac{\sin^{2} (5 lim_{x \to 0} x) \cdot lim_{x \to 0} \cos (5 x)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.5

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

$5 \frac{\sin^{2} (5 lim_{x \to 0} x) \cdot \cos (lim_{x \to 0} 5 x)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.6

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 \frac{\sin^{2} (5 lim_{x \to 0} x) \cdot \cos (5 lim_{x \to 0} x)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.7

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

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Step 3.1.2.7.1

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

$5 \frac{\sin^{2} (5 \cdot 0) \cdot \cos (5 lim_{x \to 0} x)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.7.2

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

$5 \frac{\sin^{2} (5 \cdot 0) \cdot \cos (5 \cdot 0)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.8

Simplify the answer.

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Step 3.1.2.8.1

Multiply $5$ by $0$ .

$5 \frac{\sin^{2} (0) \cdot \cos (5 \cdot 0)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.8.2

The exact value of $\sin (0)$ is $0$ .

$5 \frac{0^{2} \cdot \cos (5 \cdot 0)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.8.3

Raising $0$ to any positive power yields $0$ .

$5 \frac{0 \cdot \cos (5 \cdot 0)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.8.4

Multiply $5$ by $0$ .

$5 \frac{0 \cdot \cos (0)}{lim_{x \to 0} x^{2}}$

Step 3.1.2.8.5

The exact value of $\cos (0)$ is $1$ .

$5 \frac{0 \cdot 1}{lim_{x \to 0} x^{2}}$

Step 3.1.2.8.6

Multiply $0$ by $1$ .

$5 \frac{0}{lim_{x \to 0} x^{2}}$

Step 3.1.3

Evaluate the limit of the denominator.

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Step 3.1.3.1

Move the exponent $2$ from $x^{2}$ outside the limit using the Limits Power Rule.

$5 \frac{0}{{(lim_{x \to 0} x)}^{2}}$

Step 3.1.3.2

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

$5 \frac{0}{0^{2}}$

Step 3.1.3.3

Raising $0$ to any positive power yields $0$ .

$5 (\frac{0}{0})$

Step 3.1.3.4

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

Undefined

$5 (\frac{0}{0})$

Step 3.1.4

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

Undefined

$5 (\frac{0}{0})$

Step 3.2

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.

$lim_{x \to 0} \frac{\sin^{2} (5 x) \cos (5 x)}{x^{2}} = lim_{x \to 0} \frac{\frac{d}{d x} [\sin^{2} (5 x) \cos (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3

Find the derivative of the numerator and denominator.

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Step 3.3.1

Differentiate the numerator and denominator.

$5 lim_{x \to 0} \frac{\frac{d}{d x} [\sin^{2} (5 x) \cos (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = \sin^{2} (5 x)$ and $g (x) = \cos (5 x)$ .

$5 lim_{x \to 0} \frac{\sin^{2} (5 x) \frac{d}{d x} [\cos (5 x)] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \cos (x)$ and $g (x) = 5 x$ .

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Step 3.3.3.1

To apply the Chain Rule, set $u_{1}$ as $5 x$ .

$5 lim_{x \to 0} \frac{\sin^{2} (5 x) \frac{d}{d u_{1}} [\cos (u_{1})] \frac{d}{d x} [5 x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.3.2

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

$5 lim_{x \to 0} \frac{\sin^{2} (5 x) \cdot - 1 \sin (u_{1}) \frac{d}{d x} [5 x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.3.3

Replace all occurrences of $u_{1}$ with $5 x$ .

$5 lim_{x \to 0} \frac{\sin^{2} (5 x) \cdot - 1 \sin (5 x) \frac{d}{d x} [5 x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.4

Multiply $\sin^{2} (5 x)$ by $\sin (5 x)$ by adding the exponents.

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Step 3.3.4.1

Move $\sin (5 x)$ .

$5 lim_{x \to 0} \frac{\sin (5 x) \sin^{2} (5 x) \cdot - 1 \frac{d}{d x} [5 x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.4.2

Multiply $\sin (5 x)$ by $\sin^{2} (5 x)$ .

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Step 3.3.4.2.1

Raise $\sin (5 x)$ to the power of $1$ .

$5 lim_{x \to 0} \frac{\sin^{1} (5 x) \sin^{2} (5 x) \cdot - 1 \frac{d}{d x} [5 x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.4.2.2

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

$5 lim_{x \to 0} \frac{{\sin (5 x)}^{1 + 2} \cdot - 1 \frac{d}{d x} [5 x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.4.3

Add $1$ and $2$ .

$5 lim_{x \to 0} \frac{\sin^{3} (5 x) \cdot - 1 \frac{d}{d x} [5 x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.5

Since $5$ is constant with respect to $x$ , the derivative of $5 x$ with respect to $x$ is $5 \frac{d}{d x} [x]$ .

$5 lim_{x \to 0} \frac{\sin^{3} (5 x) \cdot - 1 \cdot 5 \frac{d}{d x} [x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.6

Multiply $5$ by $- 1$ .

$5 lim_{x \to 0} \frac{\sin^{3} (5 x) \cdot - 5 \frac{d}{d x} [x] + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.7

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

$5 lim_{x \to 0} \frac{\sin^{3} (5 x) \cdot - 5 \cdot 1 + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.8

Multiply $- 5$ by $1$ .

$5 lim_{x \to 0} \frac{\sin^{3} (5 x) \cdot - 5 + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.9

Move $- 5$ to the left of $\sin^{3} (5 x)$ .

$5 lim_{x \to 0} \frac{- 5 \cdot \sin^{3} (5 x) + \cos (5 x) \frac{d}{d x} [\sin^{2} (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.10

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{2}$ and $g (x) = \sin (5 x)$ .

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Step 3.3.10.1

To apply the Chain Rule, set $u_{2}$ as $\sin (5 x)$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + \cos (5 x) \frac{d}{d u_{2}} [{u_{2}}^{2}] \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.10.2

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

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + \cos (5 x) \cdot 2 u_{2} \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.10.3

Replace all occurrences of $u_{2}$ with $\sin (5 x)$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + \cos (5 x) \cdot 2 \sin (5 x) \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.11

Move $2$ to the left of $\cos (5 x)$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 \cdot \cos (5 x) \sin (5 x) \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.12

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \sin (x)$ and $g (x) = 5 x$ .

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Step 3.3.12.1

To apply the Chain Rule, set $u_{3}$ as $5 x$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 \cos (5 x) \sin (5 x) \frac{d}{d u_{3}} [\sin (u_{3})] \frac{d}{d x} [5 x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.12.2

The derivative of $\sin (u_{3})$ with respect to $u_{3}$ is $\cos (u_{3})$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 \cos (5 x) \sin (5 x) \cos (u_{3}) \frac{d}{d x} [5 x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.12.3

Replace all occurrences of $u_{3}$ with $5 x$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 \cos (5 x) \sin (5 x) \cos (5 x) \frac{d}{d x} [5 x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.13

Raise $\cos (5 x)$ to the power of $1$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 \cos^{1} (5 x) \cos (5 x) \sin (5 x) \frac{d}{d x} [5 x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.14

Raise $\cos (5 x)$ to the power of $1$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 \cos^{1} (5 x) \cos^{1} (5 x) \sin (5 x) \frac{d}{d x} [5 x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.15

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

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 {\cos (5 x)}^{1 + 1} \sin (5 x) \frac{d}{d x} [5 x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.16

Add $1$ and $1$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 \cos^{2} (5 x) \sin (5 x) \frac{d}{d x} [5 x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.17

Since $5$ is constant with respect to $x$ , the derivative of $5 x$ with respect to $x$ is $5 \frac{d}{d x} [x]$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 2 \cos^{2} (5 x) \sin (5 x) \cdot 5 \frac{d}{d x} [x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.18

Multiply $5$ by $2$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 10 \cos^{2} (5 x) \sin (5 x) \frac{d}{d x} [x]}{\frac{d}{d x} [x^{2}]}$

Step 3.3.19

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

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 10 \cos^{2} (5 x) \sin (5 x) \cdot 1}{\frac{d}{d x} [x^{2}]}$

Step 3.3.20

Multiply $10$ by $1$ .

$5 lim_{x \to 0} \frac{- 5 \sin^{3} (5 x) + 10 \cos^{2} (5 x) \sin (5 x)}{\frac{d}{d x} [x^{2}]}$

Step 3.3.21

Reorder terms.

$5 lim_{x \to 0} \frac{10 \cos^{2} (5 x) \sin (5 x) - 5 \sin^{3} (5 x)}{\frac{d}{d x} [x^{2}]}$

Step 3.3.22

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

$5 lim_{x \to 0} \frac{10 \cos^{2} (5 x) \sin (5 x) - 5 \sin^{3} (5 x)}{2 x}$

Step 4

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 \cos^{2} (5 x) \sin (5 x) - 5 \sin^{3} (5 x)}{x}$

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.

$5 (\frac{1}{2}) \frac{lim_{x \to 0} 10 \cos^{2} (5 x) \sin (5 x) - 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2

Evaluate the limit of the numerator.

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Step 5.1.2.1

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

$5 (\frac{1}{2}) \frac{lim_{x \to 0} 10 \cos^{2} (5 x) \sin (5 x) - lim_{x \to 0} 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.2

Move the term $10$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) \frac{10 lim_{x \to 0} \cos^{2} (5 x) \sin (5 x) - lim_{x \to 0} 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.3

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

$5 (\frac{1}{2}) \frac{10 lim_{x \to 0} \cos^{2} (5 x) \cdot lim_{x \to 0} \sin (5 x) - lim_{x \to 0} 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.4

Move the exponent $2$ from $\cos^{2} (5 x)$ outside the limit using the Limits Power Rule.

$5 (\frac{1}{2}) \frac{10 {(lim_{x \to 0} \cos (5 x))}^{2} \cdot lim_{x \to 0} \sin (5 x) - lim_{x \to 0} 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.5

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

$5 (\frac{1}{2}) \frac{10 \cos^{2} (lim_{x \to 0} 5 x) \cdot lim_{x \to 0} \sin (5 x) - lim_{x \to 0} 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.6

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 lim_{x \to 0} x) \cdot lim_{x \to 0} \sin (5 x) - lim_{x \to 0} 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.7

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

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 lim_{x \to 0} x) \cdot \sin (lim_{x \to 0} 5 x) - lim_{x \to 0} 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.8

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 lim_{x \to 0} x) \cdot \sin (5 lim_{x \to 0} x) - lim_{x \to 0} 5 \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.9

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 lim_{x \to 0} x) \cdot \sin (5 lim_{x \to 0} x) - 5 lim_{x \to 0} \sin^{3} (5 x)}{lim_{x \to 0} x}$

Step 5.1.2.10

Move the exponent $3$ from $\sin^{3} (5 x)$ outside the limit using the Limits Power Rule.

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 lim_{x \to 0} x) \cdot \sin (5 lim_{x \to 0} x) - 5 {(lim_{x \to 0} \sin (5 x))}^{3}}{lim_{x \to 0} x}$

Step 5.1.2.11

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

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 lim_{x \to 0} x) \cdot \sin (5 lim_{x \to 0} x) - 5 \sin^{3} (lim_{x \to 0} 5 x)}{lim_{x \to 0} x}$

Step 5.1.2.12

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 lim_{x \to 0} x) \cdot \sin (5 lim_{x \to 0} x) - 5 \sin^{3} (5 lim_{x \to 0} x)}{lim_{x \to 0} x}$

Step 5.1.2.13

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

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Step 5.1.2.13.1

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

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 \cdot 0) \cdot \sin (5 lim_{x \to 0} x) - 5 \sin^{3} (5 lim_{x \to 0} x)}{lim_{x \to 0} x}$

Step 5.1.2.13.2

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

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 \cdot 0) \cdot \sin (5 \cdot 0) - 5 \sin^{3} (5 lim_{x \to 0} x)}{lim_{x \to 0} x}$

Step 5.1.2.13.3

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

$5 (\frac{1}{2}) \frac{10 \cos^{2} (5 \cdot 0) \cdot \sin (5 \cdot 0) - 5 \sin^{3} (5 \cdot 0)}{lim_{x \to 0} x}$

Step 5.1.2.14

Simplify the answer.

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Step 5.1.2.14.1

Simplify each term.

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Step 5.1.2.14.1.1

Multiply $5$ by $0$ .

$5 (\frac{1}{2}) \frac{10 \cos^{2} (0) \cdot \sin (5 \cdot 0) - 5 \sin^{3} (5 \cdot 0)}{lim_{x \to 0} x}$

Step 5.1.2.14.1.2

The exact value of $\cos (0)$ is $1$ .

$5 (\frac{1}{2}) \frac{10 \cdot 1^{2} \cdot \sin (5 \cdot 0) - 5 \sin^{3} (5 \cdot 0)}{lim_{x \to 0} x}$

Step 5.1.2.14.1.3

One to any power is one.

$5 (\frac{1}{2}) \frac{10 \cdot 1 \cdot \sin (5 \cdot 0) - 5 \sin^{3} (5 \cdot 0)}{lim_{x \to 0} x}$

Step 5.1.2.14.1.4

Multiply $10$ by $1$ .

$5 (\frac{1}{2}) \frac{10 \cdot \sin (5 \cdot 0) - 5 \sin^{3} (5 \cdot 0)}{lim_{x \to 0} x}$

Step 5.1.2.14.1.5

Multiply $5$ by $0$ .

$5 (\frac{1}{2}) \frac{10 \cdot \sin (0) - 5 \sin^{3} (5 \cdot 0)}{lim_{x \to 0} x}$

Step 5.1.2.14.1.6

The exact value of $\sin (0)$ is $0$ .

$5 (\frac{1}{2}) \frac{10 \cdot 0 - 5 \sin^{3} (5 \cdot 0)}{lim_{x \to 0} x}$

Step 5.1.2.14.1.7

Multiply $10$ by $0$ .

$5 (\frac{1}{2}) \frac{0 - 5 \sin^{3} (5 \cdot 0)}{lim_{x \to 0} x}$

Step 5.1.2.14.1.8

Multiply $5$ by $0$ .

$5 (\frac{1}{2}) \frac{0 - 5 \sin^{3} (0)}{lim_{x \to 0} x}$

Step 5.1.2.14.1.9

The exact value of $\sin (0)$ is $0$ .

$5 (\frac{1}{2}) \frac{0 - 5 \cdot 0^{3}}{lim_{x \to 0} x}$

Step 5.1.2.14.1.10

Raising $0$ to any positive power yields $0$ .

$5 (\frac{1}{2}) \frac{0 - 5 \cdot 0}{lim_{x \to 0} x}$

Step 5.1.2.14.1.11

Multiply $- 5$ by $0$ .

$5 (\frac{1}{2}) \frac{0 + 0}{lim_{x \to 0} x}$

Step 5.1.2.14.2

Add $0$ and $0$ .

$5 (\frac{1}{2}) \frac{0}{lim_{x \to 0} x}$

Step 5.1.3

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

$5 (\frac{1}{2}) \frac{0}{0}$

Step 5.1.4

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

Undefined

$5 (\frac{1}{2}) \frac{0}{0}$

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.

$lim_{x \to 0} \frac{10 \cos^{2} (5 x) \sin (5 x) - 5 \sin^{3} (5 x)}{x} = lim_{x \to 0} \frac{\frac{d}{d x} [10 \cos^{2} (5 x) \sin (5 x) - 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3

Find the derivative of the numerator and denominator.

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Step 5.3.1

Differentiate the numerator and denominator.

$5 (\frac{1}{2}) lim_{x \to 0} \frac{\frac{d}{d x} [10 \cos^{2} (5 x) \sin (5 x) - 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.2

By the Sum Rule, the derivative of $10 \cos^{2} (5 x) \sin (5 x) - 5 \sin^{3} (5 x)$ with respect to $x$ is $\frac{d}{d x} [10 \cos^{2} (5 x) \sin (5 x)] + \frac{d}{d x} [- 5 \sin^{3} (5 x)]$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{\frac{d}{d x} [10 \cos^{2} (5 x) \sin (5 x)] + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3

Evaluate $\frac{d}{d x} [10 \cos^{2} (5 x) \sin (5 x)]$ .

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Step 5.3.3.1

Since $10$ is constant with respect to $x$ , the derivative of $10 \cos^{2} (5 x) \sin (5 x)$ with respect to $x$ is $10 \frac{d}{d x} [\cos^{2} (5 x) \sin (5 x)]$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 \frac{d}{d x} [\cos^{2} (5 x) \sin (5 x)] + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = \cos^{2} (5 x)$ and $g (x) = \sin (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \frac{d}{d x} [\sin (5 x)] + \sin (5 x) \frac{d}{d x} [\cos^{2} (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \sin (x)$ and $g (x) = 5 x$ .

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Step 5.3.3.3.1

To apply the Chain Rule, set $u_{1}$ as $5 x$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \frac{d}{d u_{1}} [\sin (u_{1})] \frac{d}{d x} [5 x] + \sin (5 x) \frac{d}{d x} [\cos^{2} (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.3.2

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (u_{1}) \frac{d}{d x} [5 x] + \sin (5 x) \frac{d}{d x} [\cos^{2} (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.3.3

Replace all occurrences of $u_{1}$ with $5 x$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \frac{d}{d x} [5 x] + \sin (5 x) \frac{d}{d x} [\cos^{2} (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.4

Since $5$ is constant with respect to $x$ , the derivative of $5 x$ with respect to $x$ is $5 \frac{d}{d x} [x]$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \frac{d}{d x} [x] + \sin (5 x) \frac{d}{d x} [\cos^{2} (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.5

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \frac{d}{d x} [\cos^{2} (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.6

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{2}$ and $g (x) = \cos (5 x)$ .

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Step 5.3.3.6.1

To apply the Chain Rule, set $u_{2}$ as $\cos (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \frac{d}{d u_{2}} [{u_{2}}^{2}] \frac{d}{d x} [\cos (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.6.2

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \cdot 2 u_{2} \frac{d}{d x} [\cos (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.6.3

Replace all occurrences of $u_{2}$ with $\cos (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \cdot 2 \cos (5 x) \frac{d}{d x} [\cos (5 x)]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.7

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \cos (x)$ and $g (x) = 5 x$ .

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Step 5.3.3.7.1

To apply the Chain Rule, set $u_{3}$ as $5 x$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \cdot 2 \cos (5 x) \frac{d}{d u_{3}} [\cos (u_{3})] \frac{d}{d x} [5 x]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.7.2

The derivative of $\cos (u_{3})$ with respect to $u_{3}$ is $- \sin (u_{3})$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (u_{3}) \frac{d}{d x} [5 x]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.7.3

Replace all occurrences of $u_{3}$ with $5 x$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \frac{d}{d x} [5 x]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.8

Since $5$ is constant with respect to $x$ , the derivative of $5 x$ with respect to $x$ is $5 \frac{d}{d x} [x]$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \frac{d}{d x} [x]) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.9

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \cdot 1) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.10

Multiply $5$ by $1$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cos (5 x) \cdot 5 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \cdot 1) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.11

Move $5$ to the left of $\cos (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{2} (5 x) \cdot 5 \cdot \cos (5 x) + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \cdot 1) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.12

Multiply $\cos^{2} (5 x)$ by $\cos (5 x)$ by adding the exponents.

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Step 5.3.3.12.1

Move $\cos (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos (5 x) \cos^{2} (5 x) \cdot 5 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \cdot 1) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.12.2

Multiply $\cos (5 x)$ by $\cos^{2} (5 x)$ .

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Step 5.3.3.12.2.1

Raise $\cos (5 x)$ to the power of $1$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{1} (5 x) \cos^{2} (5 x) \cdot 5 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \cdot 1) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.12.2.2

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 ({\cos (5 x)}^{1 + 2} \cdot 5 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \cdot 1) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.12.3

Add $1$ and $2$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (\cos^{3} (5 x) \cdot 5 + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \cdot 1) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.13

Move $5$ to the left of $\cos^{3} (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cdot \cos^{3} (5 x) + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5 \cdot 1) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.14

Multiply $5$ by $1$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 1 \sin (5 x) \cdot 5) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.15

Multiply $5$ by $- 1$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) + \sin (5 x) \cdot 2 \cos (5 x) \cdot - 5 \sin (5 x)) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.16

Multiply $- 5$ by $2$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) + \sin (5 x) \cdot - 10 \cos (5 x) \sin (5 x)) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.17

Raise $\sin (5 x)$ to the power of $1$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{1} (5 x) \sin (5 x)) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.18

Raise $\sin (5 x)$ to the power of $1$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{1} (5 x) \sin^{1} (5 x)) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.19

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) {\sin (5 x)}^{1 + 1}) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.3.20

Add $1$ and $1$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) + \frac{d}{d x} [- 5 \sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.4

Evaluate $\frac{d}{d x} [- 5 \sin^{3} (5 x)]$ .

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Step 5.3.4.1

Since $- 5$ is constant with respect to $x$ , the derivative of $- 5 \sin^{3} (5 x)$ with respect to $x$ is $- 5 \frac{d}{d x} [\sin^{3} (5 x)]$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \frac{d}{d x} [\sin^{3} (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.4.2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{3}$ and $g (x) = \sin (5 x)$ .

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Step 5.3.4.2.1

To apply the Chain Rule, set $u_{4}$ as $\sin (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \frac{d}{d u_{4}} [{u_{4}}^{3}] \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.4.2.2

Differentiate using the Power Rule which states that $\frac{d}{d u_{4}} [{u_{4}}^{n}]$ is $n {u_{4}}^{n - 1}$ where $n = 3$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 {u_{4}}^{2} \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.4.2.3

Replace all occurrences of $u_{4}$ with $\sin (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 \sin^{2} (5 x) \frac{d}{d x} [\sin (5 x)]}{\frac{d}{d x} [x]}$

Step 5.3.4.3

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \sin (x)$ and $g (x) = 5 x$ .

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Step 5.3.4.3.1

To apply the Chain Rule, set $u_{5}$ as $5 x$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 \sin^{2} (5 x) \frac{d}{d u_{5}} [\sin (u_{5})] \frac{d}{d x} [5 x]}{\frac{d}{d x} [x]}$

Step 5.3.4.3.2

The derivative of $\sin (u_{5})$ with respect to $u_{5}$ is $\cos (u_{5})$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 \sin^{2} (5 x) \cos (u_{5}) \frac{d}{d x} [5 x]}{\frac{d}{d x} [x]}$

Step 5.3.4.3.3

Replace all occurrences of $u_{5}$ with $5 x$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 \sin^{2} (5 x) \cos (5 x) \frac{d}{d x} [5 x]}{\frac{d}{d x} [x]}$

Step 5.3.4.4

Since $5$ is constant with respect to $x$ , the derivative of $5 x$ with respect to $x$ is $5 \frac{d}{d x} [x]$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 \sin^{2} (5 x) \cos (5 x) \cdot 5 \frac{d}{d x} [x]}{\frac{d}{d x} [x]}$

Step 5.3.4.5

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 \sin^{2} (5 x) \cos (5 x) \cdot 5 \cdot 1}{\frac{d}{d x} [x]}$

Step 5.3.4.6

Multiply $5$ by $1$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 \sin^{2} (5 x) \cos (5 x) \cdot 5}{\frac{d}{d x} [x]}$

Step 5.3.4.7

Move $5$ to the left of $\cos (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 3 \sin^{2} (5 x) \cdot 5 \cdot \cos (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.4.8

Multiply $5$ by $3$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 5 \cdot 15 \sin^{2} (5 x) \cos (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.4.9

Multiply $15$ by $- 5$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 (5 \cos^{3} (5 x) - 10 \cos (5 x) \sin^{2} (5 x)) - 75 \sin^{2} (5 x) \cos (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.5

Simplify.

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Step 5.3.5.1

Apply the distributive property.

$5 (\frac{1}{2}) lim_{x \to 0} \frac{10 \cdot 5 \cos^{3} (5 x) + 10 \cdot - 10 \cos (5 x) \sin^{2} (5 x) - 75 \sin^{2} (5 x) \cos (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.5.2

Combine terms.

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Step 5.3.5.2.1

Multiply $5$ by $10$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{50 \cos^{3} (5 x) + 10 \cdot - 10 \cos (5 x) \sin^{2} (5 x) - 75 \sin^{2} (5 x) \cos (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.5.2.2

Multiply $- 10$ by $10$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{50 \cos^{3} (5 x) - 100 \cos (5 x) \sin^{2} (5 x) - 75 \sin^{2} (5 x) \cos (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.5.2.3

Reorder the factors of $- 100 \cos (5 x) \sin^{2} (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{50 \cos^{3} (5 x) - 100 \sin^{2} (5 x) \cos (5 x) - 75 \sin^{2} (5 x) \cos (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.5.2.4

Subtract $75 \sin^{2} (5 x) \cos (5 x)$ from $- 100 \sin^{2} (5 x) \cos (5 x)$ .

$5 (\frac{1}{2}) lim_{x \to 0} \frac{50 \cos^{3} (5 x) - 175 \sin^{2} (5 x) \cos (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.5.3

Reorder terms.

$5 (\frac{1}{2}) lim_{x \to 0} \frac{- 175 \sin^{2} (5 x) \cos (5 x) + 50 \cos^{3} (5 x)}{\frac{d}{d x} [x]}$

Step 5.3.6

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

$5 (\frac{1}{2}) lim_{x \to 0} \frac{- 175 \sin^{2} (5 x) \cos (5 x) + 50 \cos^{3} (5 x)}{1}$

Step 5.4

Divide $- 175 \sin^{2} (5 x) \cos (5 x) + 50 \cos^{3} (5 x)$ by $1$ .

$5 (\frac{1}{2}) lim_{x \to 0} - 175 \sin^{2} (5 x) \cos (5 x) + 50 \cos^{3} (5 x)$

Step 6

Evaluate the limit.

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Step 6.1

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

$5 (\frac{1}{2}) (- lim_{x \to 0} 175 \sin^{2} (5 x) \cos (5 x) + lim_{x \to 0} 50 \cos^{3} (5 x))$

Step 6.2

Move the term $175$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) (- 175 lim_{x \to 0} \sin^{2} (5 x) \cos (5 x) + lim_{x \to 0} 50 \cos^{3} (5 x))$

Step 6.3

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

$5 (\frac{1}{2}) (- 175 lim_{x \to 0} \sin^{2} (5 x) \cdot lim_{x \to 0} \cos (5 x) + lim_{x \to 0} 50 \cos^{3} (5 x))$

Step 6.4

Move the exponent $2$ from $\sin^{2} (5 x)$ outside the limit using the Limits Power Rule.

$5 (\frac{1}{2}) (- 175 {(lim_{x \to 0} \sin (5 x))}^{2} \cdot lim_{x \to 0} \cos (5 x) + lim_{x \to 0} 50 \cos^{3} (5 x))$

Step 6.5

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

$5 (\frac{1}{2}) (- 175 \sin^{2} (lim_{x \to 0} 5 x) \cdot lim_{x \to 0} \cos (5 x) + lim_{x \to 0} 50 \cos^{3} (5 x))$

Step 6.6

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 lim_{x \to 0} x) \cdot lim_{x \to 0} \cos (5 x) + lim_{x \to 0} 50 \cos^{3} (5 x))$

Step 6.7

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

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 lim_{x \to 0} x) \cdot \cos (lim_{x \to 0} 5 x) + lim_{x \to 0} 50 \cos^{3} (5 x))$

Step 6.8

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 lim_{x \to 0} x) \cdot \cos (5 lim_{x \to 0} x) + lim_{x \to 0} 50 \cos^{3} (5 x))$

Step 6.9

Move the term $50$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 lim_{x \to 0} x) \cdot \cos (5 lim_{x \to 0} x) + 50 lim_{x \to 0} \cos^{3} (5 x))$

Step 6.10

Move the exponent $3$ from $\cos^{3} (5 x)$ outside the limit using the Limits Power Rule.

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 lim_{x \to 0} x) \cdot \cos (5 lim_{x \to 0} x) + 50 {(lim_{x \to 0} \cos (5 x))}^{3})$

Step 6.11

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

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 lim_{x \to 0} x) \cdot \cos (5 lim_{x \to 0} x) + 50 \cos^{3} (lim_{x \to 0} 5 x))$

Step 6.12

Move the term $5$ outside of the limit because it is constant with respect to $x$ .

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 lim_{x \to 0} x) \cdot \cos (5 lim_{x \to 0} x) + 50 \cos^{3} (5 lim_{x \to 0} x))$

Step 7

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

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Step 7.1

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

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 \cdot 0) \cdot \cos (5 lim_{x \to 0} x) + 50 \cos^{3} (5 lim_{x \to 0} x))$

Step 7.2

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

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 \cdot 0) \cdot \cos (5 \cdot 0) + 50 \cos^{3} (5 lim_{x \to 0} x))$

Step 7.3

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

$5 (\frac{1}{2}) (- 175 \sin^{2} (5 \cdot 0) \cdot \cos (5 \cdot 0) + 50 \cos^{3} (5 \cdot 0))$

Step 8

Simplify the answer.

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Step 8.1

Combine $5$ and $\frac{1}{2}$ .

$\frac{5}{2} (- 175 \sin^{2} (5 \cdot 0) \cdot \cos (5 \cdot 0) + 50 \cos^{3} (5 \cdot 0))$

Step 8.2

Simplify each term.

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Step 8.2.1

Multiply $5$ by $0$ .

$\frac{5}{2} (- 175 \sin^{2} (0) \cdot \cos (5 \cdot 0) + 50 \cos^{3} (5 \cdot 0))$

Step 8.2.2

The exact value of $\sin (0)$ is $0$ .

$\frac{5}{2} (- 175 \cdot 0^{2} \cdot \cos (5 \cdot 0) + 50 \cos^{3} (5 \cdot 0))$

Step 8.2.3

Raising $0$ to any positive power yields $0$ .

$\frac{5}{2} (- 175 \cdot 0 \cdot \cos (5 \cdot 0) + 50 \cos^{3} (5 \cdot 0))$

Step 8.2.4

Multiply $- 175$ by $0$ .

$\frac{5}{2} (0 \cdot \cos (5 \cdot 0) + 50 \cos^{3} (5 \cdot 0))$

Step 8.2.5

Multiply $5$ by $0$ .

$\frac{5}{2} (0 \cdot \cos (0) + 50 \cos^{3} (5 \cdot 0))$

Step 8.2.6

The exact value of $\cos (0)$ is $1$ .

$\frac{5}{2} (0 \cdot 1 + 50 \cos^{3} (5 \cdot 0))$

Step 8.2.7

Multiply $0$ by $1$ .

$\frac{5}{2} (0 + 50 \cos^{3} (5 \cdot 0))$

Step 8.2.8

Multiply $5$ by $0$ .

$\frac{5}{2} (0 + 50 \cos^{3} (0))$

Step 8.2.9

The exact value of $\cos (0)$ is $1$ .

$\frac{5}{2} (0 + 50 \cdot 1^{3})$

Step 8.2.10

One to any power is one.

$\frac{5}{2} (0 + 50 \cdot 1)$

Step 8.2.11

Multiply $50$ by $1$ .

$\frac{5}{2} (0 + 50)$

Step 8.3

Add $0$ and $50$ .

$\frac{5}{2} \cdot 50$

Step 8.4

Cancel the common factor of $2$ .

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Step 8.4.1

Factor $2$ out of $50$ .

$\frac{5}{2} \cdot (2 (25))$

Step 8.4.2

Cancel the common factor.

$\frac{5}{2} \cdot (2 \cdot 25)$

Step 8.4.3

Rewrite the expression.

$5 \cdot 25$

Step 8.5

Multiply $5$ by $25$ .

$125$