Calculus Examples

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

Step 1

Since $3$ is constant with respect to $x$ , move $3$ out of the integral.

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

Step 2

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

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Step 2.1

Let $u = x^{2}$ . Find $\frac{d u}{d x}$ .

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Step 2.1.1

Differentiate $x^{2}$ .

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

Step 2.1.2

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

$2 x$

Step 2.2

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

$3 \int \cos (u) \frac{1}{2} d u$

Step 3

Combine $\cos (u)$ and $\frac{1}{2}$ .

$3 \int \frac{\cos (u)}{2} d u$

Step 4

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

$3 (\frac{1}{2} \int \cos (u) d u)$

Step 5

Combine $\frac{1}{2}$ and $3$ .

$\frac{3}{2} \int \cos (u) d u$

Step 6

The integral of $\cos (u)$ with respect to $u$ is $\sin (u)$ .

$\frac{3}{2} (\sin (u) + C)$

Step 7

Simplify.

$\frac{3}{2} \sin (u) + C$

Step 8

Replace all occurrences of $u$ with $x^{2}$ .

$\frac{3}{2} \sin (x^{2}) + C$