Calculus Examples

$\int 45 \sin^{3} (x) \cos^{2} (x) d x$

Step 1

Since $45$ is constant with respect to $x$ , move $45$ out of the integral.

$45 \int \sin^{3} (x) \cos^{2} (x) d x$

Step 2

Factor out $\sin^{2} (x)$ .

$45 \int \sin^{2} (x) \sin (x) \cos^{2} (x) d x$

Step 3

Using the Pythagorean Identity, rewrite $\sin^{2} (x)$ as $1 - \cos^{2} (x)$ .

$45 \int (1 - \cos^{2} (x)) \sin (x) \cos^{2} (x) d x$

Step 4

Let $u = \cos (x)$ . Then $d u = - \sin (x) d x$ , so $- \frac{1}{\sin (x)} d u = d x$ . Rewrite using $u$ and $d$ $u$ .

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Step 4.1

Let $u = \cos (x)$ . Find $\frac{d u}{d x}$ .

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Step 4.1.1

Differentiate $\cos (x)$ .

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

Step 4.1.2

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

$- \sin (x)$

Step 4.2

Rewrite the problem using $u$ and $d u$ .

$45 \int (- 1 + u^{2}) u^{2} d u$

Step 5

Multiply $(- 1 + u^{2}) u^{2}$ .

$45 \int - 1 u^{2} + u^{2} u^{2} d u$

Step 6

Simplify.

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Step 6.1

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

$45 \int - u^{2} + u^{2} u^{2} d u$

Step 6.2

Multiply $u^{2}$ by $u^{2}$ by adding the exponents.

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Step 6.2.1

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

$45 \int - u^{2} + u^{2 + 2} d u$

Step 6.2.2

Add $2$ and $2$ .

$45 \int - u^{2} + u^{4} d u$

Step 7

Split the single integral into multiple integrals.

$45 (\int - u^{2} d u + \int u^{4} d u)$

Step 8

Since $- 1$ is constant with respect to $u$ , move $- 1$ out of the integral.

$45 (- \int u^{2} d u + \int u^{4} d u)$

Step 9

By the Power Rule, the integral of $u^{2}$ with respect to $u$ is $\frac{1}{3} u^{3}$ .

$45 (- (\frac{1}{3} u^{3} + C) + \int u^{4} d u)$

Step 10

By the Power Rule, the integral of $u^{4}$ with respect to $u$ is $\frac{1}{5} u^{5}$ .

$45 (- (\frac{1}{3} u^{3} + C) + \frac{1}{5} u^{5} + C)$

Step 11

Simplify.

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Step 11.1

Simplify.

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Step 11.1.1

Combine $\frac{1}{3}$ and $u^{3}$ .

$45 (- (\frac{u^{3}}{3} + C) + \frac{1}{5} u^{5} + C)$

Step 11.1.2

Combine $\frac{1}{5}$ and $u^{5}$ .

$45 (- (\frac{u^{3}}{3} + C) + \frac{u^{5}}{5} + C)$

Step 11.2

Simplify.

$45 (- \frac{1}{3} u^{3} + \frac{1}{5} u^{5}) + C$

Step 12

Replace all occurrences of $u$ with $\cos (x)$ .

$45 (- \frac{1}{3} \cos^{3} (x) + \frac{1}{5} \cos^{5} (x)) + C$