Calculus Examples

$\sqrt[4]{x^{3}} \cos (x)$

Step 1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt[4]{x^{3}}$ as $x^{\frac{3}{4}}$ .

$\frac{d}{d x} [x^{\frac{3}{4}} \cos (x)]$

Step 2

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 $f (x) = x^{\frac{3}{4}}$ and $g (x) = \cos (x)$ .

$x^{\frac{3}{4}} \frac{d}{d x} [\cos (x)] + \cos (x) \frac{d}{d x} [x^{\frac{3}{4}}]$

Step 3

The derivative of $\cos (x)$ with respect to $x$ is $- \sin (x)$ .

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) \frac{d}{d x} [x^{\frac{3}{4}}]$

Step 4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = \frac{3}{4}$ .

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) (\frac{3}{4} x^{\frac{3}{4} - 1})$

Step 5

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{4}{4}$ .

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) (\frac{3}{4} x^{\frac{3}{4} - 1 \cdot \frac{4}{4}})$

Step 6

Combine $- 1$ and $\frac{4}{4}$ .

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) (\frac{3}{4} x^{\frac{3}{4} + \frac{- 1 \cdot 4}{4}})$

Step 7

Combine the numerators over the common denominator.

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) (\frac{3}{4} x^{\frac{3 - 1 \cdot 4}{4}})$

Step 8

Simplify the numerator.

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Step 8.1

Multiply $- 1$ by $4$ .

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) (\frac{3}{4} x^{\frac{3 - 4}{4}})$

Step 8.2

Subtract $4$ from $3$ .

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) (\frac{3}{4} x^{\frac{- 1}{4}})$

Step 9

Move the negative in front of the fraction.

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) (\frac{3}{4} x^{- \frac{1}{4}})$

Step 10

Combine $\frac{3}{4}$ and $x^{- \frac{1}{4}}$ .

$x^{\frac{3}{4}} (- \sin (x)) + \cos (x) \frac{3 x^{- \frac{1}{4}}}{4}$

Step 11

Combine $\cos (x)$ and $\frac{3 x^{- \frac{1}{4}}}{4}$ .

$x^{\frac{3}{4}} (- \sin (x)) + \frac{\cos (x) (3 x^{- \frac{1}{4}})}{4}$

Step 12

Simplify the expression.

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Step 12.1

Move $x^{- \frac{1}{4}}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$x^{\frac{3}{4}} (- \sin (x)) + \frac{\cos (x) \cdot 3}{4 x^{\frac{1}{4}}}$

Step 12.2

Move $3$ to the left of $\cos (x)$ .

$x^{\frac{3}{4}} (- \sin (x)) + \frac{3 \cdot \cos (x)}{4 x^{\frac{1}{4}}}$

Step 12.3

Reorder terms.

$- x^{\frac{3}{4}} \sin (x) + \frac{3 \cos (x)}{4 x^{\frac{1}{4}}}$