Calculus Examples

$\cos (\frac{1}{x})$

Step 1

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = \cos (x)$ and $g (x) = \frac{1}{x}$ .

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Step 1.1

To apply the Chain Rule, set $u$ as $\frac{1}{x}$ .

$\frac{d}{d u} [\cos (u)] \frac{d}{d x} [\frac{1}{x}]$

Step 1.2

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

$- \sin (u) \frac{d}{d x} [\frac{1}{x}]$

Step 1.3

Replace all occurrences of $u$ with $\frac{1}{x}$ .

$- \sin (\frac{1}{x}) \frac{d}{d x} [\frac{1}{x}]$

Step 2

Differentiate using the Power Rule.

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Step 2.1

Rewrite $\frac{1}{x}$ as $x^{- 1}$ .

$- \sin (\frac{1}{x}) \frac{d}{d x} [x^{- 1}]$

Step 2.2

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

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

Step 2.3

Multiply.

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Step 2.3.1

Multiply $- 1$ by $- 1$ .

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

Step 2.3.2

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

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

Step 3

Simplify.

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Step 3.1

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

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

Step 3.2

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

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