Calculus Examples

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

Step 1

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2} + y^{2}$ and $g (x) = \sin (\frac{1}{x^{2} + y^{2}})$ .

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

Step 2

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

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Step 2.1

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

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

Step 2.2

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

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

Step 2.3

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

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

Step 3

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

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

Step 4

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

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Step 4.1

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

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

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 $n = - 1$ .

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

Step 4.3

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

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

Step 5

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

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

Step 6

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

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

Step 7

Subtract $2$ from $1$ .

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

Step 8

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

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

Step 9

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

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

Step 10

Since $y^{2}$ is constant with respect to $x$ , the derivative of $y^{2}$ with respect to $x$ is $0$ .

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

Step 11

Simplify the expression.

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Step 11.1

Add $2 x$ and $0$ .

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

Step 11.2

Multiply $2$ by $- 1$ .

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

Step 12

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

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

Step 13

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

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

Step 14

Since $y^{2}$ is constant with respect to $x$ , the derivative of $y^{2}$ with respect to $x$ is $0$ .

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

Step 15

Add $2 x$ and $0$ .

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

Step 16

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

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

Step 17

Simplify.

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Step 17.1

Combine terms.

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Step 17.1.1

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

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

Step 17.1.2

Move the negative in front of the fraction.

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

Step 17.1.3

Combine $x$ and $\frac{2}{x^{2} + y^{2}}$ .

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

Step 17.1.4

Move $2$ to the left of $x$ .

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

Step 17.1.5

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

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

Step 17.1.6

To write $\sin (\frac{1}{x^{2} + y^{2}}) (2 x)$ as a fraction with a common denominator, multiply by $\frac{x^{2} + y^{2}}{x^{2} + y^{2}}$ .

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

Step 17.1.7

Combine the numerators over the common denominator.

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

Step 17.1.8

Multiply $2$ by $- 1$ .

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

Step 17.2

Reorder terms.

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