Calculus Examples

$\cos (\arctan (\ln (x)))$

Step 1

Simplify the expression.

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Step 1.1

Draw a triangle in the plane with vertices $(1, \ln (x))$ , $(1, 0)$ , and the origin. Then $\arctan (\ln (x))$ is the angle between the positive x-axis and the ray beginning at the origin and passing through $(1, \ln (x))$ . Therefore, $\cos (\arctan (\ln (x)))$ is $\frac{1}{\sqrt{1 + \ln^{2} (x)}}$ .

$\frac{d}{d x} [\frac{1}{\sqrt{1 + \ln^{2} (x)}}]$

Step 1.2

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{1 + \ln^{2} (x)}$ as ${(1 + \ln^{2} (x))}^{\frac{1}{2}}$ .

$\frac{d}{d x} [\frac{1}{{(1 + \ln^{2} (x))}^{\frac{1}{2}}}]$

Step 1.3

Rewrite $\frac{1}{{(1 + \ln^{2} (x))}^{\frac{1}{2}}}$ as ${({(1 + \ln^{2} (x))}^{\frac{1}{2}})}^{- 1}$ .

$\frac{d}{d x} [{({(1 + \ln^{2} (x))}^{\frac{1}{2}})}^{- 1}]$

Step 1.4

Multiply the exponents in ${({(1 + \ln^{2} (x))}^{\frac{1}{2}})}^{- 1}$ .

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Step 1.4.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$\frac{d}{d x} [{(1 + \ln^{2} (x))}^{\frac{1}{2} \cdot - 1}]$

Step 1.4.2

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

$\frac{d}{d x} [{(1 + \ln^{2} (x))}^{\frac{- 1}{2}}]$

Step 1.4.3

Move the negative in front of the fraction.

$\frac{d}{d x} [{(1 + \ln^{2} (x))}^{- \frac{1}{2}}]$

Step 2

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{- \frac{1}{2}}$ and $g (x) = 1 + \ln^{2} (x)$ .

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Step 2.1

To apply the Chain Rule, set $u_{1}$ as $1 + \ln^{2} (x)$ .

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

Step 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 $n = - \frac{1}{2}$ .

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

Step 2.3

Replace all occurrences of $u_{1}$ with $1 + \ln^{2} (x)$ .

$- \frac{1}{2} {(1 + \ln^{2} (x))}^{- \frac{1}{2} - 1} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 3

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$- \frac{1}{2} {(1 + \ln^{2} (x))}^{- \frac{1}{2} - 1 \cdot \frac{2}{2}} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 4

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

$- \frac{1}{2} {(1 + \ln^{2} (x))}^{- \frac{1}{2} + \frac{- 1 \cdot 2}{2}} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 5

Combine the numerators over the common denominator.

$- \frac{1}{2} {(1 + \ln^{2} (x))}^{\frac{- 1 - 1 \cdot 2}{2}} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 6

Simplify the numerator.

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Step 6.1

Multiply $- 1$ by $2$ .

$- \frac{1}{2} {(1 + \ln^{2} (x))}^{\frac{- 1 - 2}{2}} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 6.2

Subtract $2$ from $- 1$ .

$- \frac{1}{2} {(1 + \ln^{2} (x))}^{\frac{- 3}{2}} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 7

Differentiate.

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Step 7.1

Move the negative in front of the fraction.

$- \frac{1}{2} {(1 + \ln^{2} (x))}^{- \frac{3}{2}} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 7.2

Combine fractions.

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Step 7.2.1

Combine ${(1 + \ln^{2} (x))}^{- \frac{3}{2}}$ and $\frac{1}{2}$ .

$- \frac{{(1 + \ln^{2} (x))}^{- \frac{3}{2}}}{2} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 7.2.2

Move ${(1 + \ln^{2} (x))}^{- \frac{3}{2}}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$- \frac{1}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} \frac{d}{d x} [1 + \ln^{2} (x)]$

Step 7.3

By the Sum Rule, the derivative of $1 + \ln^{2} (x)$ with respect to $x$ is $\frac{d}{d x} [1] + \frac{d}{d x} [\ln^{2} (x)]$ .

$- \frac{1}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} (\frac{d}{d x} [1] + \frac{d}{d x} [\ln^{2} (x)])$

Step 7.4

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

$- \frac{1}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} (0 + \frac{d}{d x} [\ln^{2} (x)])$

Step 7.5

Add $0$ and $\frac{d}{d x} [\ln^{2} (x)]$ .

$- \frac{1}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} \frac{d}{d x} [\ln^{2} (x)]$

Step 8

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

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Step 8.1

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

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

Step 8.2

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

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

Step 8.3

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

$- \frac{1}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} (2 \ln (x) \frac{d}{d x} [\ln (x)])$

Step 9

Simplify terms.

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Step 9.1

Multiply $2$ by $- 1$ .

$- 2 \frac{1}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} (\ln (x) \frac{d}{d x} [\ln (x)])$

Step 9.2

Combine $- 2$ and $\frac{1}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}}$ .

$\frac{- 2}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} (\ln (x) \frac{d}{d x} [\ln (x)])$

Step 9.3

Combine $\ln (x)$ and $\frac{- 2}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}}$ .

$\frac{\ln (x) \cdot - 2}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} \frac{d}{d x} [\ln (x)]$

Step 9.4

Move $- 2$ to the left of $\ln (x)$ .

$\frac{- 2 \cdot \ln (x)}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} \frac{d}{d x} [\ln (x)]$

Step 9.5

Factor $2$ out of $- 2 \ln (x)$ .

$\frac{2 (- \ln (x))}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} \frac{d}{d x} [\ln (x)]$

Step 10

Cancel the common factors.

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Step 10.1

Factor $2$ out of $2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}$ .

$\frac{2 (- \ln (x))}{2 ({(1 + \ln^{2} (x))}^{\frac{3}{2}})} \frac{d}{d x} [\ln (x)]$

Step 10.2

Cancel the common factor.

$\frac{2 (- \ln (x))}{2 {(1 + \ln^{2} (x))}^{\frac{3}{2}}} \frac{d}{d x} [\ln (x)]$

Step 10.3

Rewrite the expression.

$\frac{- \ln (x)}{{(1 + \ln^{2} (x))}^{\frac{3}{2}}} \frac{d}{d x} [\ln (x)]$

Step 11

Move the negative in front of the fraction.

$- \frac{\ln (x)}{{(1 + \ln^{2} (x))}^{\frac{3}{2}}} \frac{d}{d x} [\ln (x)]$

Step 12

The derivative of $\ln (x)$ with respect to $x$ is $\frac{1}{x}$ .

$- \frac{\ln (x)}{{(1 + \ln^{2} (x))}^{\frac{3}{2}}} \cdot \frac{1}{x}$

Step 13

Multiply $\frac{1}{x}$ by $\frac{\ln (x)}{{(1 + \ln^{2} (x))}^{\frac{3}{2}}}$ .

$- \frac{\ln (x)}{x {(1 + \ln^{2} (x))}^{\frac{3}{2}}}$