Calculus Examples

$x \sqrt{1 + y^{2}} d x = y \sqrt{1 + x^{2}} d y$

Step 1

Rewrite the equation.

$y \sqrt{1 + x^{2}} d y = x \sqrt{1 + y^{2}} d x$

Step 2

Multiply both sides by $\frac{1}{\sqrt{(1 + x^{2}) (1 + y^{2})}}$ .

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

Step 3

Simplify.

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Step 3.1

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

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

Step 3.2

Combine and simplify the denominator.

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Step 3.2.1

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

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

Step 3.2.2

Raise $\sqrt{(1 + x^{2}) (1 + y^{2})}$ to the power of $1$ .

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

Step 3.2.3

Raise $\sqrt{(1 + x^{2}) (1 + y^{2})}$ to the power of $1$ .

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

Step 3.2.4

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

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

Step 3.2.5

Add $1$ and $1$ .

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

Step 3.2.6

Rewrite ${\sqrt{(1 + x^{2}) (1 + y^{2})}}^{2}$ as $(1 + x^{2}) (1 + y^{2})$ .

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Step 3.2.6.1

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

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

Step 3.2.6.2

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

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

Step 3.2.6.3

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

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

Step 3.2.6.4

Cancel the common factor of $2$ .

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Step 3.2.6.4.1

Cancel the common factor.

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

Step 3.2.6.4.2

Rewrite the expression.

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

Step 3.2.6.5

Simplify.

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

Step 3.3

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

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Step 3.3.1

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

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

Step 3.3.2

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

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

Step 3.3.3

Combine using the product rule for radicals.

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

Step 3.3.4

Raise $1 + x^{2}$ to the power of $1$ .

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

Step 3.3.5

Raise $1 + x^{2}$ to the power of $1$ .

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

Step 3.3.6

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

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

Step 3.3.7

Add $1$ and $1$ .

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

Step 3.4

Simplify the numerator.

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Step 3.4.1

Rewrite $1$ as $1^{2}$ .

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

Step 3.4.2

Pull terms out from under the radical.

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

Step 3.4.3

One to any power is one.

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

Step 3.4.4

Apply the distributive property.

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

Step 3.4.5

Multiply $\sqrt{1 + y^{2}}$ by $1$ .

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

Step 3.4.6

Factor $\sqrt{1 + y^{2}}$ out of $\sqrt{1 + y^{2}} + x^{2} \sqrt{1 + y^{2}}$ .

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Step 3.4.6.1

Multiply by $1$ .

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

Step 3.4.6.2

Factor $\sqrt{1 + y^{2}}$ out of $x^{2} \sqrt{1 + y^{2}}$ .

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

Step 3.4.6.3

Factor $\sqrt{1 + y^{2}}$ out of $\sqrt{1 + y^{2}} \cdot 1 + \sqrt{1 + y^{2}} x^{2}$ .

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

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

Step 3.5

Cancel the common factor of $1 + x^{2}$ .

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Step 3.5.1

Cancel the common factor.

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

Step 3.5.2

Rewrite the expression.

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

Step 3.6

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

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

Step 3.7

Combine and simplify the denominator.

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Step 3.7.1

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

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

Step 3.7.2

Raise $\sqrt{(1 + x^{2}) (1 + y^{2})}$ to the power of $1$ .

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

Step 3.7.3

Raise $\sqrt{(1 + x^{2}) (1 + y^{2})}$ to the power of $1$ .

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

Step 3.7.4

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

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

Step 3.7.5

Add $1$ and $1$ .

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

Step 3.7.6

Rewrite ${\sqrt{(1 + x^{2}) (1 + y^{2})}}^{2}$ as $(1 + x^{2}) (1 + y^{2})$ .

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Step 3.7.6.1

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

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

Step 3.7.6.2

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

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

Step 3.7.6.3

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

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

Step 3.7.6.4

Cancel the common factor of $2$ .

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Step 3.7.6.4.1

Cancel the common factor.

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

Step 3.7.6.4.2

Rewrite the expression.

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

Step 3.7.6.5

Simplify.

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

Step 3.8

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

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Step 3.8.1

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

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

Step 3.8.2

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

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

Step 3.8.3

Combine using the product rule for radicals.

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

Step 3.8.4

Raise $1 + y^{2}$ to the power of $1$ .

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

Step 3.8.5

Raise $1 + y^{2}$ to the power of $1$ .

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

Step 3.8.6

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

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

Step 3.8.7

Add $1$ and $1$ .

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

Step 3.9

Simplify the numerator.

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Step 3.9.1

Rewrite $1$ as $1^{2}$ .

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

Step 3.9.2

Pull terms out from under the radical.

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

Step 3.9.3

One to any power is one.

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

Step 3.9.4

Apply the distributive property.

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

Step 3.9.5

Multiply $\sqrt{1 + x^{2}}$ by $1$ .

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

Step 3.9.6

Factor $\sqrt{1 + x^{2}}$ out of $\sqrt{1 + x^{2}} + y^{2} \sqrt{1 + x^{2}}$ .

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Step 3.9.6.1

Multiply by $1$ .

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

Step 3.9.6.2

Factor $\sqrt{1 + x^{2}}$ out of $y^{2} \sqrt{1 + x^{2}}$ .

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

Step 3.9.6.3

Factor $\sqrt{1 + x^{2}}$ out of $\sqrt{1 + x^{2}} \cdot 1 + \sqrt{1 + x^{2}} y^{2}$ .

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

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

Step 3.10

Cancel the common factor of $1 + y^{2}$ .

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Step 3.10.1

Cancel the common factor.

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

Step 3.10.2

Rewrite the expression.

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

Step 4

Integrate both sides.

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Step 4.1

Set up an integral on each side.

$\int \frac{y \sqrt{1 + y^{2}}}{1 + y^{2}} d y = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2

Integrate the left side.

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Step 4.2.1

Let $u_{1} = 1 + y^{2}$ . Then $d u_{1} = 2 y d y$ , so $\frac{1}{2} d u_{1} = y d y$ . Rewrite using $u_{1}$ and $d$ $u_{1}$ .

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Step 4.2.1.1

Let $u_{1} = 1 + y^{2}$ . Find $\frac{d u_{1}}{d y}$ .

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Step 4.2.1.1.1

Differentiate $1 + y^{2}$ .

$\frac{d}{d y} [1 + y^{2}]$

Step 4.2.1.1.2

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

$\frac{d}{d y} [1] + \frac{d}{d y} [y^{2}]$

Step 4.2.1.1.3

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

$0 + \frac{d}{d y} [y^{2}]$

Step 4.2.1.1.4

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

$0 + 2 y$

Step 4.2.1.1.5

Add $0$ and $2 y$ .

$2 y$

Step 4.2.1.2

Rewrite the problem using $u_{1}$ and $d u_{1}$ .

$\int \frac{\sqrt{u_{1}}}{u_{1}} \cdot \frac{1}{2} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.2

Simplify.

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Step 4.2.2.1

Multiply $\frac{\sqrt{u_{1}}}{u_{1}}$ by $\frac{1}{2}$ .

$\int \frac{\sqrt{u_{1}}}{u_{1} \cdot 2} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.2.2

Move $2$ to the left of $u_{1}$ .

$\int \frac{\sqrt{u_{1}}}{2 u_{1}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.3

Since $\frac{1}{2}$ is constant with respect to $u_{1}$ , move $\frac{1}{2}$ out of the integral.

$\frac{1}{2} \int \frac{\sqrt{u_{1}}}{u_{1}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4

Simplify the expression.

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Step 4.2.4.1

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

$\frac{1}{2} \int \frac{{u_{1}}^{\frac{1}{2}}}{u_{1}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.2

Simplify.

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Step 4.2.4.2.1

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

$\frac{1}{2} \int \frac{1}{u_{1} \cdot {u_{1}}^{- \frac{1}{2}}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.2.2

Multiply $u_{1}$ by ${u_{1}}^{- \frac{1}{2}}$ by adding the exponents.

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Step 4.2.4.2.2.1

Multiply $u_{1}$ by ${u_{1}}^{- \frac{1}{2}}$ .

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Step 4.2.4.2.2.1.1

Raise $u_{1}$ to the power of $1$ .

$\frac{1}{2} \int \frac{1}{{u_{1}}^{1} {u_{1}}^{- \frac{1}{2}}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.2.2.1.2

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

$\frac{1}{2} \int \frac{1}{{u_{1}}^{1 - \frac{1}{2}}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.2.2.2

Write $1$ as a fraction with a common denominator.

$\frac{1}{2} \int \frac{1}{{u_{1}}^{\frac{2}{2} - \frac{1}{2}}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.2.2.3

Combine the numerators over the common denominator.

$\frac{1}{2} \int \frac{1}{{u_{1}}^{\frac{2 - 1}{2}}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.2.2.4

Subtract $1$ from $2$ .

$\frac{1}{2} \int \frac{1}{{u_{1}}^{\frac{1}{2}}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.3

Apply basic rules of exponents.

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Step 4.2.4.3.1

Move ${u_{1}}^{\frac{1}{2}}$ out of the denominator by raising it to the $- 1$ power.

$\frac{1}{2} \int {({u_{1}}^{\frac{1}{2}})}^{- 1} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.3.2

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

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Step 4.2.4.3.2.1

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

$\frac{1}{2} \int {u_{1}}^{\frac{1}{2} \cdot - 1} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.3.2.2

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

$\frac{1}{2} \int {u_{1}}^{\frac{- 1}{2}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.4.3.2.3

Move the negative in front of the fraction.

$\frac{1}{2} \int {u_{1}}^{- \frac{1}{2}} d u_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.5

By the Power Rule, the integral of ${u_{1}}^{- \frac{1}{2}}$ with respect to $u_{1}$ is $2 {u_{1}}^{\frac{1}{2}}$ .

$\frac{1}{2} (2 {u_{1}}^{\frac{1}{2}} + C_{1}) = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.6

Simplify.

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Step 4.2.6.1

Rewrite $\frac{1}{2} (2 {u_{1}}^{\frac{1}{2}} + C_{1})$ as $\frac{1}{2} \cdot 2 {u_{1}}^{\frac{1}{2}} + C_{1}$ .

$\frac{1}{2} \cdot 2 {u_{1}}^{\frac{1}{2}} + C_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.6.2

Simplify.

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Step 4.2.6.2.1

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

$\frac{2}{2} {u_{1}}^{\frac{1}{2}} + C_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.6.2.2

Cancel the common factor of $2$ .

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Step 4.2.6.2.2.1

Cancel the common factor.

$\frac{2}{2} {u_{1}}^{\frac{1}{2}} + C_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.6.2.2.2

Rewrite the expression.

$1 {u_{1}}^{\frac{1}{2}} + C_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.6.2.3

Multiply ${u_{1}}^{\frac{1}{2}}$ by $1$ .

${u_{1}}^{\frac{1}{2}} + C_{1} = \int \frac{x \sqrt{1 + x^{2}}}{1 + x^{2}} d x$

Step 4.2.7

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

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

Step 4.3

Integrate the right side.

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Step 4.3.1

Let $u_{2} = 1 + x^{2}$ . Then $d u_{2} = 2 x d x$ , so $\frac{1}{2} d u_{2} = x d x$ . Rewrite using $u_{2}$ and $d$ $u_{2}$ .

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Step 4.3.1.1

Let $u_{2} = 1 + x^{2}$ . Find $\frac{d u_{2}}{d x}$ .

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Step 4.3.1.1.1

Differentiate $1 + x^{2}$ .

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

Step 4.3.1.1.2

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

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

Step 4.3.1.1.3

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

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

Step 4.3.1.1.4

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

$0 + 2 x$

Step 4.3.1.1.5

Add $0$ and $2 x$ .

$2 x$

Step 4.3.1.2

Rewrite the problem using $u_{2}$ and $d u_{2}$ .

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \int \frac{\sqrt{u_{2}}}{u_{2}} \cdot \frac{1}{2} d u_{2}$

Step 4.3.2

Simplify.

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Step 4.3.2.1

Multiply $\frac{\sqrt{u_{2}}}{u_{2}}$ by $\frac{1}{2}$ .

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \int \frac{\sqrt{u_{2}}}{u_{2} \cdot 2} d u_{2}$

Step 4.3.2.2

Move $2$ to the left of $u_{2}$ .

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \int \frac{\sqrt{u_{2}}}{2 u_{2}} d u_{2}$

Step 4.3.3

Since $\frac{1}{2}$ is constant with respect to $u_{2}$ , move $\frac{1}{2}$ out of the integral.

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int \frac{\sqrt{u_{2}}}{u_{2}} d u_{2}$

Step 4.3.4

Simplify the expression.

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Step 4.3.4.1

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

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int \frac{{u_{2}}^{\frac{1}{2}}}{u_{2}} d u_{2}$

Step 4.3.4.2

Simplify.

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Step 4.3.4.2.1

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

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int \frac{1}{u_{2} \cdot {u_{2}}^{- \frac{1}{2}}} d u_{2}$

Step 4.3.4.2.2

Multiply $u_{2}$ by ${u_{2}}^{- \frac{1}{2}}$ by adding the exponents.

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Step 4.3.4.2.2.1

Multiply $u_{2}$ by ${u_{2}}^{- \frac{1}{2}}$ .

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Step 4.3.4.2.2.1.1

Raise $u_{2}$ to the power of $1$ .

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int \frac{1}{{u_{2}}^{1} {u_{2}}^{- \frac{1}{2}}} d u_{2}$

Step 4.3.4.2.2.1.2

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

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int \frac{1}{{u_{2}}^{1 - \frac{1}{2}}} d u_{2}$

Step 4.3.4.2.2.2

Write $1$ as a fraction with a common denominator.

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int \frac{1}{{u_{2}}^{\frac{2}{2} - \frac{1}{2}}} d u_{2}$

Step 4.3.4.2.2.3

Combine the numerators over the common denominator.

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int \frac{1}{{u_{2}}^{\frac{2 - 1}{2}}} d u_{2}$

Step 4.3.4.2.2.4

Subtract $1$ from $2$ .

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int \frac{1}{{u_{2}}^{\frac{1}{2}}} d u_{2}$

Step 4.3.4.3

Apply basic rules of exponents.

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Step 4.3.4.3.1

Move ${u_{2}}^{\frac{1}{2}}$ out of the denominator by raising it to the $- 1$ power.

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int {({u_{2}}^{\frac{1}{2}})}^{- 1} d u_{2}$

Step 4.3.4.3.2

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

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Step 4.3.4.3.2.1

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

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int {u_{2}}^{\frac{1}{2} \cdot - 1} d u_{2}$

Step 4.3.4.3.2.2

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

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int {u_{2}}^{\frac{- 1}{2}} d u_{2}$

Step 4.3.4.3.2.3

Move the negative in front of the fraction.

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \int {u_{2}}^{- \frac{1}{2}} d u_{2}$

Step 4.3.5

By the Power Rule, the integral of ${u_{2}}^{- \frac{1}{2}}$ with respect to $u_{2}$ is $2 {u_{2}}^{\frac{1}{2}}$ .

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} (2 {u_{2}}^{\frac{1}{2}} + C_{2})$

Step 4.3.6

Simplify.

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Step 4.3.6.1

Rewrite $\frac{1}{2} (2 {u_{2}}^{\frac{1}{2}} + C_{2})$ as $\frac{1}{2} \cdot 2 {u_{2}}^{\frac{1}{2}} + C_{2}$ .

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{1}{2} \cdot 2 {u_{2}}^{\frac{1}{2}} + C_{2}$

Step 4.3.6.2

Simplify.

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Step 4.3.6.2.1

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

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{2}{2} {u_{2}}^{\frac{1}{2}} + C_{2}$

Step 4.3.6.2.2

Cancel the common factor of $2$ .

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Step 4.3.6.2.2.1

Cancel the common factor.

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = \frac{2}{2} {u_{2}}^{\frac{1}{2}} + C_{2}$

Step 4.3.6.2.2.2

Rewrite the expression.

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = 1 {u_{2}}^{\frac{1}{2}} + C_{2}$

Step 4.3.6.2.3

Multiply ${u_{2}}^{\frac{1}{2}}$ by $1$ .

${(1 + y^{2})}^{\frac{1}{2}} + C_{1} = {u_{2}}^{\frac{1}{2}} + C_{2}$

Step 4.3.7

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

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

Step 4.4

Group the constant of integration on the right side as $K$ .

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