Calculus Examples

$\int e^{4 x} \sin (5 x) d x$

Step 1

Reorder $e^{4 x}$ and $\sin (5 x)$ .

$\int \sin (5 x) e^{4 x} d x$

Step 2

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = \sin (5 x)$ and $d v = e^{4 x}$ .

$\sin (5 x) (\frac{1}{4} e^{4 x}) - \int \frac{1}{4} e^{4 x} (5 \cos (5 x)) d x$

Step 3

Since $\frac{1}{4} \cdot 5$ is constant with respect to $x$ , move $\frac{1}{4} \cdot 5$ out of the integral.

$\sin (5 x) (\frac{1}{4} e^{4 x}) - (\frac{1}{4} \cdot 5 \int e^{4 x} (\cos (5 x)) d x)$

Step 4

Combine fractions.

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Step 4.1

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

$\sin (5 x) \frac{e^{4 x}}{4} - (\frac{1}{4} \cdot 5 \int e^{4 x} (\cos (5 x)) d x)$

Step 4.2

Combine $\sin (5 x)$ and $\frac{e^{4 x}}{4}$ .

$\frac{\sin (5 x) e^{4 x}}{4} - (\frac{1}{4} \cdot 5 \int e^{4 x} (\cos (5 x)) d x)$

Step 4.3

Combine $\frac{1}{4}$ and $5$ .

$\frac{\sin (5 x) e^{4 x}}{4} - (\frac{5}{4} \int e^{4 x} (\cos (5 x)) d x)$

Step 4.4

Reorder $e^{4 x}$ and $\cos (5 x)$ .

$\frac{\sin (5 x) e^{4 x}}{4} - (\frac{5}{4} \int \cos (5 x) e^{4 x} d x)$

Step 5

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = \cos (5 x)$ and $d v = e^{4 x}$ .

$\frac{\sin (5 x) e^{4 x}}{4} - (\frac{5}{4} (\cos (5 x) (\frac{1}{4} e^{4 x}) - \int \frac{1}{4} e^{4 x} (- 5 \sin (5 x)) d x))$

Step 6

Since $\frac{1}{4} \cdot - 5$ is constant with respect to $x$ , move $\frac{1}{4} \cdot - 5$ out of the integral.

$\frac{\sin (5 x) e^{4 x}}{4} - (\frac{5}{4} (\cos (5 x) (\frac{1}{4} e^{4 x}) - (\frac{1}{4} \cdot - 5 \int e^{4 x} (\sin (5 x)) d x)))$

Step 7

Simplify terms.

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Step 7.1

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

$\frac{\sin (5 x) e^{4 x}}{4} - (\frac{5}{4} (\cos (5 x) \frac{e^{4 x}}{4} - (\frac{1}{4} \cdot - 5 \int e^{4 x} (\sin (5 x)) d x)))$

Step 7.2

Combine $\cos (5 x)$ and $\frac{e^{4 x}}{4}$ .

$\frac{\sin (5 x) e^{4 x}}{4} - (\frac{5}{4} (\frac{\cos (5 x) e^{4 x}}{4} - (\frac{1}{4} \cdot - 5 \int e^{4 x} (\sin (5 x)) d x)))$

Step 7.3

Combine $\frac{1}{4}$ and $- 5$ .

$\frac{\sin (5 x) e^{4 x}}{4} - (\frac{5}{4} (\frac{\cos (5 x) e^{4 x}}{4} - (\frac{- 5}{4} \int e^{4 x} (\sin (5 x)) d x)))$

Step 7.4

Apply the distributive property.

$\frac{\sin (5 x) e^{4 x}}{4} - \frac{5}{4} \cdot \frac{\cos (5 x) e^{4 x}}{4} - \frac{5}{4} (- (\frac{- 5}{4} \int e^{4 x} (\sin (5 x)) d x))$

Step 7.5

Multiply $\frac{\cos (5 x) e^{4 x}}{4}$ by $\frac{5}{4}$ .

$\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{4 \cdot 4} - \frac{5}{4} (- (\frac{- 5}{4} \int e^{4 x} (\sin (5 x)) d x))$

Step 7.6

Multiply.

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Step 7.6.1

Multiply $4$ by $4$ .

$\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{16} - \frac{5}{4} (- (\frac{- 5}{4} \int e^{4 x} (\sin (5 x)) d x))$

Step 7.6.2

Multiply $- 1$ by $- 1$ .

$\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{16} + 1 (\frac{5}{4}) (\frac{- 5}{4} \int e^{4 x} (\sin (5 x)) d x)$

Step 7.6.3

Multiply $\frac{5}{4}$ by $1$ .

$\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{16} + \frac{5}{4} (\frac{- 5}{4} \int e^{4 x} (\sin (5 x)) d x)$

Step 7.7

Multiply $\frac{- 5}{4}$ by $\frac{5}{4}$ .

$\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{16} + \frac{- 5 \cdot 5}{4 \cdot 4} \int e^{4 x} (\sin (5 x)) d x$

Step 7.8

Multiply.

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Step 7.8.1

Multiply $- 5$ by $5$ .

$\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{16} + \frac{- 25}{4 \cdot 4} \int e^{4 x} (\sin (5 x)) d x$

Step 7.8.2

Multiply $4$ by $4$ .

$\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{16} + \frac{- 25}{16} \int e^{4 x} (\sin (5 x)) d x$

Step 8

Solving for $\int e^{4 x} \sin (5 x) d x$ , we find that $\int e^{4 x} \sin (5 x) d x$ = $\frac{\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{16}}{\frac{41}{16}}$ .

$\frac{\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) e^{4 x} \cdot 5}{16}}{\frac{41}{16}} + C$

Step 9

Simplify the answer.

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Step 9.1

Simplify.

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Step 9.1.1

Move $5$ to the left of $\cos (5 x) e^{4 x}$ .

$\frac{\frac{\sin (5 x) e^{4 x}}{4} - \frac{5 \cdot (\cos (5 x) e^{4 x})}{16}}{\frac{41}{16}} + C$

Step 9.1.2

Multiply by the reciprocal of the fraction to divide by $\frac{41}{16}$ .

$(\frac{\sin (5 x) e^{4 x}}{4} - \frac{5 \cos (5 x) e^{4 x}}{16}) \frac{16}{41} + C$

Step 9.2

Rewrite $(\frac{\sin (5 x) e^{4 x}}{4} - \frac{5 \cos (5 x) e^{4 x}}{16}) \frac{16}{41} + C$ as $(\frac{1}{4} \sin (5 x) e^{4 x} - \frac{5}{16} \cos (5 x) e^{4 x}) \frac{16}{41} + C$ .

$(\frac{1}{4} \sin (5 x) e^{4 x} - \frac{5}{16} \cos (5 x) e^{4 x}) \frac{16}{41} + C$

Step 9.3

Simplify.

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Step 9.3.1

Combine $\frac{1}{4}$ and $\sin (5 x)$ .

$(\frac{\sin (5 x)}{4} e^{4 x} - \frac{5}{16} \cos (5 x) e^{4 x}) \frac{16}{41} + C$

Step 9.3.2

Combine $\frac{\sin (5 x)}{4}$ and $e^{4 x}$ .

$(\frac{\sin (5 x) e^{4 x}}{4} - \frac{5}{16} \cos (5 x) e^{4 x}) \frac{16}{41} + C$

Step 9.3.3

Combine $\cos (5 x)$ and $\frac{5}{16}$ .

$(\frac{\sin (5 x) e^{4 x}}{4} - \frac{\cos (5 x) \cdot 5}{16} e^{4 x}) \frac{16}{41} + C$

Step 9.3.4

Combine $e^{4 x}$ and $\frac{\cos (5 x) \cdot 5}{16}$ .

$(\frac{\sin (5 x) e^{4 x}}{4} - \frac{e^{4 x} (\cos (5 x) \cdot 5)}{16}) \frac{16}{41} + C$

Step 9.3.5

Move $5$ to the left of $\cos (5 x)$ .

$(\frac{\sin (5 x) e^{4 x}}{4} - \frac{e^{4 x} (5 \cos (5 x))}{16}) \frac{16}{41} + C$

Step 9.4

Simplify.

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Step 9.4.1

Reorder factors in $\frac{\sin (5 x) e^{4 x}}{4}$ .

$(\frac{e^{4 x} \sin (5 x)}{4} - \frac{e^{4 x} (5 \cos (5 x))}{16}) \frac{16}{41} + C$

Step 9.4.2

Simplify the numerator.

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Step 9.4.2.1

Rewrite.

$(\frac{e^{4 x} \sin (5 x)}{4} - \frac{e^{4 x} (\cos (5 x) \cdot 5)}{16}) \frac{16}{41} + C$

Step 9.4.2.2

Move $5$ to the left of $\cos (5 x)$ .

$(\frac{e^{4 x} \sin (5 x)}{4} - \frac{e^{4 x} (5 \cdot \cos (5 x))}{16}) \frac{16}{41} + C$

Step 9.4.2.3

Remove unnecessary parentheses.

$(\frac{e^{4 x} \sin (5 x)}{4} - \frac{e^{4 x} \cdot 5 \cos (5 x)}{16}) \frac{16}{41} + C$

Step 9.4.3

Move $5$ to the left of $e^{4 x}$ .

$(\frac{1}{4} e^{4 x} \sin (5 x) - \frac{5}{16} e^{4 x} \cos (5 x)) \frac{16}{41} + C$