Calculus Examples

\int \cos (3 x) d x

$\int \cos (3 x) d x$

Step 1

Let

u = 3 x

$u = 3 x$ . Then

d u = 3 d x

$d u = 3 d x$ , so

\frac{1}{3} d u = d x

$\frac{1}{3} d u = d x$ . Rewrite using

u

$u$ and

d

$d$

u

$u$ .

Tap for more steps...

Step 1.1

Let

u = 3 x

$u = 3 x$ . Find

\frac{d u}{d x}

$\frac{d u}{d x}$ .

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Step 1.1.1

Differentiate

3 x

$3 x$ .

\frac{d}{d x} [3 x]

$\frac{d}{d x} [3 x]$

Step 1.1.2

Since

3

$3$ is constant with respect to

x

$x$ , the derivative of

3 x

$3 x$ with respect to

x

$x$ is

3 \frac{d}{d x} [x]

$3 \frac{d}{d x} [x]$ .

3 \frac{d}{d x} [x]

$3 \frac{d}{d x} [x]$

Step 1.1.3

Differentiate using the Power Rule which states that

\frac{d}{d x} [x^{n}]

$\frac{d}{d x} [x^{n}]$ is

n x^{n - 1}

$n x^{n - 1}$ where

n = 1

$n = 1$ .

3 \cdot 1

$3 \cdot 1$

Step 1.1.4

Multiply

3

$3$ by

1

$1$ .

3

$3$

3

$3$

Step 1.2

Rewrite the problem using

u

$u$ and

d u

$d u$ .

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

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

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

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

Step 2

Combine

\cos (u)

$\cos (u)$ and

\frac{1}{3}

$\frac{1}{3}$ .

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

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

Step 3

Since

\frac{1}{3}

$\frac{1}{3}$ is constant with respect to

u

$u$ , move

\frac{1}{3}

$\frac{1}{3}$ out of the integral.

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

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

Step 4

The integral of

\cos (u)

$\cos (u)$ with respect to

u

$u$ is

\sin (u)

$\sin (u)$ .

\frac{1}{3} (\sin (u) + C)

$\frac{1}{3} (\sin (u) + C)$

Step 5

Simplify.

\frac{1}{3} \sin (u) + C

$\frac{1}{3} \sin (u) + C$

Step 6

Replace all occurrences of

u

$u$ with

3 x

$3 x$ .

\frac{1}{3} \sin (3 x) + C

$\frac{1}{3} \sin (3 x) + C$

\int_{}^{} \cos 3 x

$\int_{}^{} \cos 3 x$

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[\begin{array}{c} x^{2} & \frac{1}{2} \\ \sqrt{π} & \int x d x \end{array}]

$[\begin{array}{c} x^{2} & \frac{1}{2} \\ \sqrt{π} & \int x d x \end{array}]$