Calculus Examples

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

Step 1

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

$y = \ln (x + {(1 + x^{2})}^{\frac{1}{2}})$

Step 2

Differentiate both sides of the equation.

$\frac{d}{d x} (y) = \frac{d}{d x} (\ln (x + {(1 + x^{2})}^{\frac{1}{2}}))$

Step 3

The derivative of $y$ with respect to $x$ is $y'$ .

$y'$

Step 4

Differentiate the right side of the equation.

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Step 4.1

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

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Step 4.1.1

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

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

Step 4.1.2

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

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

Step 4.1.3

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

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

Step 4.2

Differentiate.

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Step 4.2.1

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

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

Step 4.2.2

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

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

Step 4.3

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

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Step 4.3.1

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

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

Step 4.3.2

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

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

Step 4.3.3

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

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

Step 4.4

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

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

Step 4.5

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

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

Step 4.6

Combine the numerators over the common denominator.

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

Step 4.7

Simplify the numerator.

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Step 4.7.1

Multiply $- 1$ by $2$ .

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

Step 4.7.2

Subtract $2$ from $1$ .

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

Step 4.8

Combine fractions.

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Step 4.8.1

Move the negative in front of the fraction.

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

Step 4.8.2

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

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

Step 4.8.3

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

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

Step 4.9

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

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

Step 4.10

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

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

Step 4.11

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

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

Step 4.12

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

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

Step 4.13

Simplify terms.

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Step 4.13.1

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

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

Step 4.13.2

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

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

Step 4.13.3

Cancel the common factor.

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

Step 4.13.4

Rewrite the expression.

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

Step 4.14

Simplify.

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Step 4.14.1

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

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

Step 4.14.2

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

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

Step 4.14.3

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

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Step 4.14.3.1

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

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

Step 4.14.3.2

Combine.

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

Step 4.14.4

Apply the distributive property.

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

Step 4.14.5

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

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Step 4.14.5.1

Cancel the common factor.

Step 4.14.5.2

Rewrite the expression.

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

Step 4.14.6

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

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

Step 4.14.7

Simplify the denominator.

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Step 4.14.7.1

Multiply ${(1 + x^{2})}^{\frac{1}{2}}$ by ${(1 + x^{2})}^{\frac{1}{2}}$ by adding the exponents.

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Step 4.14.7.1.1

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

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

Step 4.14.7.1.2

Combine the numerators over the common denominator.

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

Step 4.14.7.1.3

Add $1$ and $1$ .

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

Step 4.14.7.1.4

Divide $2$ by $2$ .

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

Step 4.14.7.2

Simplify ${(1 + x^{2})}^{1}$ .

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

Step 4.14.7.3

Reorder terms.

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

Step 5

Reform the equation by setting the left side equal to the right side.

$y' = \frac{{(1 + x^{2})}^{\frac{1}{2}} + x}{x^{2} + x {(1 + x^{2})}^{\frac{1}{2}} + 1}$

Step 6

Replace $y'$ with $\frac{d y}{d x}$ .

$\frac{d y}{d x} = \frac{{(1 + x^{2})}^{\frac{1}{2}} + x}{x^{2} + x {(1 + x^{2})}^{\frac{1}{2}} + 1}$