Calculus Examples

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

Step 1

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

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

Step 2

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

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Step 2.1

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

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

Step 2.2

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

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

Step 3

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

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Step 3.1

Since $- 1$ is constant with respect to $x$ , the derivative of $- \cos^{2} (x)$ with respect to $x$ is $- \frac{d}{d x} [\cos^{2} (x)]$ .

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

Step 3.2

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

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Step 3.2.1

To apply the Chain Rule, set $u$ as $\cos (x)$ .

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

Step 3.2.2

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

$2 \cos (x) - (2 u \frac{d}{d x} [\cos (x)])$

Step 3.2.3

Replace all occurrences of $u$ with $\cos (x)$ .

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

Step 3.3

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

$2 \cos (x) - (2 \cos (x) (- \sin (x)))$

Step 3.4

Multiply $- 1$ by $2$ .

$2 \cos (x) - (- 2 \cos (x) \sin (x))$

Step 3.5

Multiply $- 2$ by $- 1$ .

$2 \cos (x) + 2 \cos (x) \sin (x)$

Step 4

Simplify.

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Step 4.1

Reorder terms.

$2 \cos (x) \sin (x) + 2 \cos (x)$

Step 4.2

Simplify each term.

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Step 4.2.1

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

$\sin (x) (2 \cos (x)) + 2 \cos (x)$

Step 4.2.2

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

$2 \cdot \sin (x) \cos (x) + 2 \cos (x)$

Step 4.2.3

Apply the sine double-angle identity.

$\sin (2 x) + 2 \cos (x)$