Calculus Examples

$y = x^{2} \sin^{4} (x) + \cos^{- 2} (x)$

Step 1

By the Sum Rule, the derivative of $x^{2} \sin^{4} (x) + \cos^{- 2} (x)$ with respect to $x$ is $\frac{d}{d x} [x^{2} \sin^{4} (x)] + \frac{d}{d x} [\cos^{- 2} (x)]$ .

$\frac{d}{d x} [x^{2} \sin^{4} (x)] + \frac{d}{d x} [\cos^{- 2} (x)]$

Step 2

Evaluate $\frac{d}{d x} [x^{2} \sin^{4} (x)]$ .

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Step 2.1

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 $f (x) = x^{2}$ and $g (x) = \sin^{4} (x)$ .

$x^{2} \frac{d}{d x} [\sin^{4} (x)] + \sin^{4} (x) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [\cos^{- 2} (x)]$

Step 2.2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{4}$ and $g (x) = \sin (x)$ .

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Step 2.2.1

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

$x^{2} (\frac{d}{d u_{1}} [{u_{1}}^{4}] \frac{d}{d x} [\sin (x)]) + \sin^{4} (x) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [\cos^{- 2} (x)]$

Step 2.2.2

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

$x^{2} (4 {u_{1}}^{3} \frac{d}{d x} [\sin (x)]) + \sin^{4} (x) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [\cos^{- 2} (x)]$

Step 2.2.3

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

$x^{2} (4 \sin^{3} (x) \frac{d}{d x} [\sin (x)]) + \sin^{4} (x) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [\cos^{- 2} (x)]$

Step 2.3

The derivative of $\sin (x)$ with respect to $x$ is $\cos (x)$ .

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [\cos^{- 2} (x)]$

Step 2.4

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

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) (2 x) + \frac{d}{d x} [\cos^{- 2} (x)]$

Step 3

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

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Step 3.1

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 $g (x) = \cos (x)$ .

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Step 3.1.1

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

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) (2 x) + \frac{d}{d u_{2}} [{u_{2}}^{- 2}] \frac{d}{d x} [\cos (x)]$

Step 3.1.2

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

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) (2 x) - 2 {u_{2}}^{- 3} \frac{d}{d x} [\cos (x)]$

Step 3.1.3

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

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) (2 x) - 2 \cos^{- 3} (x) \frac{d}{d x} [\cos (x)]$

Step 3.2

The derivative of $\cos (x)$ with respect to $x$ is $- \sin (x)$ .

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) (2 x) - 2 \cos^{- 3} (x) (- \sin (x))$

Step 3.3

Multiply $- 1$ by $- 2$ .

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) (2 x) + 2 \cos^{- 3} (x) \sin (x)$

Step 4

Simplify.

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Step 4.1

Rewrite the expression using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) (2 x) + 2 \frac{1}{\cos^{3} (x)} \sin (x)$

Step 4.2

Convert from $\frac{1}{\cos^{3} (x)}$ to $\sec^{3} (x)$ .

$x^{2} (4 \sin^{3} (x) \cos (x)) + \sin^{4} (x) (2 x) + 2 \sec^{3} (x) \sin (x)$

Step 4.3

Reorder terms.

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + 2 \sec^{3} (x) \sin (x)$

Step 4.4

Simplify each term.

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Step 4.4.1

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

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + 2 {(\frac{1}{\cos (x)})}^{3} \sin (x)$

Step 4.4.2

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

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + 2 \frac{1^{3}}{\cos^{3} (x)} \sin (x)$

Step 4.4.3

One to any power is one.

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + 2 \frac{1}{\cos^{3} (x)} \sin (x)$

Step 4.4.4

Combine $2$ and $\frac{1}{\cos^{3} (x)}$ .

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + \frac{2}{\cos^{3} (x)} \sin (x)$

Step 4.4.5

Combine $\frac{2}{\cos^{3} (x)}$ and $\sin (x)$ .

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + \frac{2 \sin (x)}{\cos^{3} (x)}$

Step 4.5

Simplify each term.

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Step 4.5.1

Factor $\cos (x)$ out of $\cos^{3} (x)$ .

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + \frac{2 \sin (x)}{\cos (x) \cos^{2} (x)}$

Step 4.5.2

Separate fractions.

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + \frac{2}{\cos^{2} (x)} \cdot \frac{\sin (x)}{\cos (x)}$

Step 4.5.3

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

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + \frac{2}{\cos^{2} (x)} \tan (x)$

Step 4.5.4

Multiply by $1$ .

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + \frac{2}{\cos^{2} (x) \cdot 1} \tan (x)$

Step 4.5.5

Separate fractions.

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + \frac{2}{1} \cdot \frac{1}{\cos^{2} (x)} \tan (x)$

Step 4.5.6

Convert from $\frac{1}{\cos^{2} (x)}$ to $\sec^{2} (x)$ .

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + \frac{2}{1} \sec^{2} (x) \tan (x)$

Step 4.5.7

Divide $2$ by $1$ .

$4 x^{2} \sin^{3} (x) \cos (x) + 2 x \sin^{4} (x) + 2 \sec^{2} (x) \tan (x)$