Calculus Examples

$f (x) = \ln (x + \sqrt{x^{2} - 1})$

Step 1

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

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

Step 2

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

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Step 2.1

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

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

Step 2.2

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

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

Step 2.3

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

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

Step 3

Differentiate.

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Step 3.1

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

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

Step 3.2

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

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

Step 4

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 $g (x) = x^{2} - 1$ .

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Step 4.1

To apply the Chain Rule, set $u_{2}$ as $x^{2} - 1$ .

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

Step 4.2

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

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

Step 4.3

Replace all occurrences of $u_{2}$ with $x^{2} - 1$ .

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

Step 5

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

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

Step 6

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

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

Step 7

Combine the numerators over the common denominator.

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

Step 8

Simplify the numerator.

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Step 8.1

Multiply $- 1$ by $2$ .

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

Step 8.2

Subtract $2$ from $1$ .

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

Step 9

Combine fractions.

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Step 9.1

Move the negative in front of the fraction.

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

Step 9.2

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

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

Step 9.3

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

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

Step 10

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

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

Step 11

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

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

Step 12

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

$\frac{1}{x + {(x^{2} - 1)}^{\frac{1}{2}}} (1 + \frac{1}{2 {(x^{2} - 1)}^{\frac{1}{2}}} (2 x + 0))$

Step 13

Simplify terms.

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Step 13.1

Add $2 x$ and $0$ .

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

Step 13.2

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

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

Step 13.3

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

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

Step 13.4

Cancel the common factor.

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

Step 13.5

Rewrite the expression.

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

Step 14

Simplify.

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Step 14.1

Reorder the factors of $\frac{1}{x + {(x^{2} - 1)}^{\frac{1}{2}}} (1 + \frac{x}{{(x^{2} - 1)}^{\frac{1}{2}}})$ .

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

Step 14.2

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

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

Step 14.3

Multiply the numerator and denominator of the fraction by ${(x^{2} - 1)}^{\frac{1}{2}}$ .

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Step 14.3.1

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

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

Step 14.3.2

Combine.

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

Step 14.4

Apply the distributive property.

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

Step 14.5

Cancel the common factor of ${(x^{2} - 1)}^{\frac{1}{2}}$ .

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Step 14.5.1

Cancel the common factor.

Step 14.5.2

Rewrite the expression.

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

Step 14.6

Multiply ${(x^{2} - 1)}^{\frac{1}{2}}$ by $1$ .

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

Step 14.7

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

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Step 14.7.1

Reorder ${(x^{2} - 1)}^{\frac{1}{2}}$ and $x$ .

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

Step 14.7.2

Factor ${(x^{2} - 1)}^{\frac{1}{2}}$ out of $x {(x^{2} - 1)}^{\frac{1}{2}}$ .

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

Step 14.7.3

Factor ${(x^{2} - 1)}^{\frac{1}{2}}$ out of ${(x^{2} - 1)}^{\frac{1}{2}} {(x^{2} - 1)}^{\frac{1}{2}}$ .

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

Step 14.7.4

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

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

Step 14.8

Reorder terms.

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

Step 14.9

Cancel the common factor.

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

Step 14.10

Rewrite the expression.

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