Calculus Examples

$\frac{d y}{d x} = 3 \cos (6 x)$

Step 1

Rewrite the equation.

$d y = 3 \cos (6 x) d x$

Step 2

Integrate both sides.

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Step 2.1

Set up an integral on each side.

$\int d y = \int 3 \cos (6 x) d x$

Step 2.2

Apply the constant rule.

$y + C_{1} = \int 3 \cos (6 x) d x$

Step 2.3

Integrate the right side.

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Step 2.3.1

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

$y + C_{1} = 3 \int \cos (6 x) d x$

Step 2.3.2

Let $u = 6 x$ . Then $d u = 6 d x$ , so $\frac{1}{6} d u = d x$ . Rewrite using $u$ and $d$ $u$ .

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Step 2.3.2.1

Let $u = 6 x$ . Find $\frac{d u}{d x}$ .

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Step 2.3.2.1.1

Differentiate $6 x$ .

$\frac{d}{d x} [6 x]$

Step 2.3.2.1.2

Since $6$ is constant with respect to $x$ , the derivative of $6 x$ with respect to $x$ is $6 \frac{d}{d x} [x]$ .

$6 \frac{d}{d x} [x]$

Step 2.3.2.1.3

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

$6 \cdot 1$

Step 2.3.2.1.4

Multiply $6$ by $1$ .

$6$

Step 2.3.2.2

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

$y + C_{1} = 3 \int \cos (u) \frac{1}{6} d u$

Step 2.3.3

Combine $\cos (u)$ and $\frac{1}{6}$ .

$y + C_{1} = 3 \int \frac{\cos (u)}{6} d u$

Step 2.3.4

Since $\frac{1}{6}$ is constant with respect to $u$ , move $\frac{1}{6}$ out of the integral.

$y + C_{1} = 3 (\frac{1}{6} \int \cos (u) d u)$

Step 2.3.5

Simplify.

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Step 2.3.5.1

Combine $\frac{1}{6}$ and $3$ .

$y + C_{1} = \frac{3}{6} \int \cos (u) d u$

Step 2.3.5.2

Cancel the common factor of $3$ and $6$ .

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Step 2.3.5.2.1

Factor $3$ out of $3$ .

$y + C_{1} = \frac{3 (1)}{6} \int \cos (u) d u$

Step 2.3.5.2.2

Cancel the common factors.

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Step 2.3.5.2.2.1

Factor $3$ out of $6$ .

$y + C_{1} = \frac{3 \cdot 1}{3 \cdot 2} \int \cos (u) d u$

Step 2.3.5.2.2.2

Cancel the common factor.

$y + C_{1} = \frac{3 \cdot 1}{3 \cdot 2} \int \cos (u) d u$

Step 2.3.5.2.2.3

Rewrite the expression.

$y + C_{1} = \frac{1}{2} \int \cos (u) d u$

Step 2.3.6

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

$y + C_{1} = \frac{1}{2} (\sin (u) + C_{2})$

Step 2.3.7

Simplify.

$y + C_{1} = \frac{1}{2} \sin (u) + C_{2}$

Step 2.3.8

Replace all occurrences of $u$ with $6 x$ .

$y + C_{1} = \frac{1}{2} \sin (6 x) + C_{2}$

Step 2.4

Group the constant of integration on the right side as $K$ .

$y = \frac{1}{2} \sin (6 x) + K$