Calculus Examples

$\frac{d y}{d x} + 2 y = \sin (x)$

Step 1

The integrating factor is defined by the formula $e^{\int P (x) d x}$ , where $P (x) = 2$ .

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Step 1.1

Set up the integration.

$e^{\int 2 d x}$

Step 1.2

Apply the constant rule.

$e^{2 x + C}$

Step 1.3

Remove the constant of integration.

$e^{2 x}$

Step 2

Multiply each term by the integrating factor $e^{2 x}$ .

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Step 2.1

Multiply each term by $e^{2 x}$ .

$e^{2 x} \frac{d y}{d x} + e^{2 x} (2 y) = e^{2 x} \sin (x)$

Step 2.2

Rewrite using the commutative property of multiplication.

$e^{2 x} \frac{d y}{d x} + 2 e^{2 x} y = e^{2 x} \sin (x)$

Step 2.3

Reorder factors in $e^{2 x} \frac{d y}{d x} + 2 e^{2 x} y = e^{2 x} \sin (x)$ .

$e^{2 x} \frac{d y}{d x} + 2 y e^{2 x} = e^{2 x} \sin (x)$

Step 3

Rewrite the left side as a result of differentiating a product.

$\frac{d}{d x} [e^{2 x} y] = e^{2 x} \sin (x)$

Step 4

Set up an integral on each side.

$\int \frac{d}{d x} [e^{2 x} y] d x = \int e^{2 x} \sin (x) d x$

Step 5

Integrate the left side.

$e^{2 x} y = \int e^{2 x} \sin (x) d x$

Step 6

Integrate the right side.

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Step 6.1

Reorder $e^{2 x}$ and $\sin (x)$ .

$e^{2 x} y = \int \sin (x) e^{2 x} d x$

Step 6.2

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = \sin (x)$ and $d v = e^{2 x}$ .

$e^{2 x} y = \sin (x) (\frac{1}{2} e^{2 x}) - \int \frac{1}{2} e^{2 x} \cos (x) d x$

Step 6.3

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

$e^{2 x} y = \sin (x) (\frac{1}{2} e^{2 x}) - (\frac{1}{2} \int e^{2 x} \cos (x) d x)$

Step 6.4

Combine fractions.

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Step 6.4.1

Combine $\frac{1}{2}$ and $e^{2 x}$ .

$e^{2 x} y = \sin (x) \frac{e^{2 x}}{2} - (\frac{1}{2} \int e^{2 x} \cos (x) d x)$

Step 6.4.2

Combine $\sin (x)$ and $\frac{e^{2 x}}{2}$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - (\frac{1}{2} \int e^{2 x} \cos (x) d x)$

Step 6.4.3

Reorder $e^{2 x}$ and $\cos (x)$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - (\frac{1}{2} \int \cos (x) e^{2 x} d x)$

Step 6.5

Integrate by parts using the formula $\int u d v = u v - \int v d u$ , where $u = \cos (x)$ and $d v = e^{2 x}$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - (\frac{1}{2} (\cos (x) (\frac{1}{2} e^{2 x}) - \int \frac{1}{2} e^{2 x} (- \sin (x)) d x))$

Step 6.6

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

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - (\frac{1}{2} (\cos (x) (\frac{1}{2} e^{2 x}) - (\frac{1}{2} \cdot - 1 \int e^{2 x} (\sin (x)) d x)))$

Step 6.7

Simplify terms.

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Step 6.7.1

Combine $\frac{1}{2}$ and $e^{2 x}$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - (\frac{1}{2} (\cos (x) \frac{e^{2 x}}{2} - (\frac{1}{2} \cdot - 1 \int e^{2 x} (\sin (x)) d x)))$

Step 6.7.2

Combine $\cos (x)$ and $\frac{e^{2 x}}{2}$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - (\frac{1}{2} (\frac{\cos (x) e^{2 x}}{2} - (\frac{1}{2} \cdot - 1 \int e^{2 x} (\sin (x)) d x)))$

Step 6.7.3

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

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - (\frac{1}{2} (\frac{\cos (x) e^{2 x}}{2} - (\frac{- 1}{2} \int e^{2 x} (\sin (x)) d x)))$

Step 6.7.4

Apply the distributive property.

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - \frac{1}{2} \cdot \frac{\cos (x) e^{2 x}}{2} - \frac{1}{2} (- (\frac{- 1}{2} \int e^{2 x} (\sin (x)) d x))$

Step 6.7.5

Multiply $\frac{\cos (x) e^{2 x}}{2}$ by $\frac{1}{2}$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{2 \cdot 2} - \frac{1}{2} (- (\frac{- 1}{2} \int e^{2 x} (\sin (x)) d x))$

Step 6.7.6

Multiply.

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Step 6.7.6.1

Multiply $2$ by $2$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4} - \frac{1}{2} (- (\frac{- 1}{2} \int e^{2 x} (\sin (x)) d x))$

Step 6.7.6.2

Multiply $- 1$ by $- 1$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4} + 1 (\frac{1}{2}) (\frac{- 1}{2} \int e^{2 x} (\sin (x)) d x)$

Step 6.7.6.3

Multiply $\frac{1}{2}$ by $1$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4} + \frac{1}{2} (\frac{- 1}{2} \int e^{2 x} (\sin (x)) d x)$

Step 6.7.7

Multiply $\frac{- 1}{2}$ by $\frac{1}{2}$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4} + \frac{- 1}{2 \cdot 2} \int e^{2 x} (\sin (x)) d x$

Step 6.7.8

Multiply $2$ by $2$ .

$e^{2 x} y = \frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4} + \frac{- 1}{4} \int e^{2 x} (\sin (x)) d x$

Step 6.8

Solving for $\int e^{2 x} \sin (x) d x$ , we find that $\int e^{2 x} \sin (x) d x$ = $\frac{\frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4}}{\frac{5}{4}}$ .

$e^{2 x} y = \frac{\frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4}}{\frac{5}{4}} + C$

Step 6.9

Simplify the answer.

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Step 6.9.1

Multiply by the reciprocal of the fraction to divide by $\frac{5}{4}$ .

$e^{2 x} y = (\frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4}) \frac{4}{5} + C$

Step 6.9.2

Rewrite $(\frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x) e^{2 x}}{4}) \frac{4}{5} + C$ as $(\frac{1}{2} \sin (x) e^{2 x} - \frac{1}{4} \cos (x) e^{2 x}) \frac{4}{5} + C$ .

$e^{2 x} y = (\frac{1}{2} \sin (x) e^{2 x} - \frac{1}{4} \cos (x) e^{2 x}) \frac{4}{5} + C$

Step 6.9.3

Simplify.

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Step 6.9.3.1

Combine $\frac{1}{2}$ and $\sin (x)$ .

$e^{2 x} y = (\frac{\sin (x)}{2} e^{2 x} - \frac{1}{4} \cos (x) e^{2 x}) \frac{4}{5} + C$

Step 6.9.3.2

Combine $\frac{\sin (x)}{2}$ and $e^{2 x}$ .

$e^{2 x} y = (\frac{\sin (x) e^{2 x}}{2} - \frac{1}{4} \cos (x) e^{2 x}) \frac{4}{5} + C$

Step 6.9.3.3

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

$e^{2 x} y = (\frac{\sin (x) e^{2 x}}{2} - \frac{\cos (x)}{4} e^{2 x}) \frac{4}{5} + C$

Step 6.9.3.4

Combine $e^{2 x}$ and $\frac{\cos (x)}{4}$ .

$e^{2 x} y = (\frac{\sin (x) e^{2 x}}{2} - \frac{e^{2 x} \cos (x)}{4}) \frac{4}{5} + C$

Step 6.9.4

Reorder factors in $\frac{\sin (x) e^{2 x}}{2}$ .

$e^{2 x} y = (\frac{1}{2} e^{2 x} \sin (x) - \frac{1}{4} e^{2 x} \cos (x)) \frac{4}{5} + C$

Step 7

Solve for $y$ .

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Step 7.1

Simplify.

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Step 7.1.1

Combine $e^{2 x}$ and $\frac{1}{4}$ .

$e^{2 x} y = (\frac{1}{2} \cdot (e^{2 x} \sin (x)) - \frac{e^{2 x}}{4} \cdot \cos (x)) \frac{4}{5} + C$

Step 7.1.2

Combine $\cos (x)$ and $\frac{e^{2 x}}{4}$ .

$e^{2 x} y = (\frac{1}{2} \cdot (e^{2 x} \sin (x)) - \frac{\cos (x) e^{2 x}}{4}) \frac{4}{5} + C$

Step 7.1.3

Remove parentheses.

$e^{2 x} y = (\frac{1}{2} \cdot e^{2 x} \sin (x) - \frac{\cos (x) e^{2 x}}{4}) \frac{4}{5} + C$

Step 7.2

Divide each term in $e^{2 x} y = (\frac{1}{2} \cdot (e^{2 x} \sin (x)) - \frac{\cos (x) e^{2 x}}{4}) (\frac{4}{5}) + C$ by $e^{2 x}$ and simplify.

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Step 7.2.1

Divide each term in $e^{2 x} y = (\frac{1}{2} \cdot (e^{2 x} \sin (x)) - \frac{\cos (x) e^{2 x}}{4}) (\frac{4}{5}) + C$ by $e^{2 x}$ .

$\frac{e^{2 x} y}{e^{2 x}} = \frac{(\frac{1}{2} \cdot (e^{2 x} \sin (x)) - \frac{\cos (x) e^{2 x}}{4}) (\frac{4}{5})}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.2

Simplify the left side.

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Step 7.2.2.1

Cancel the common factor of $e^{2 x}$ .

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Step 7.2.2.1.1

Cancel the common factor.

$\frac{e^{2 x} y}{e^{2 x}} = \frac{(\frac{1}{2} \cdot (e^{2 x} \sin (x)) - \frac{\cos (x) e^{2 x}}{4}) (\frac{4}{5})}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.2.1.2

Divide $y$ by $1$ .

$y = \frac{(\frac{1}{2} \cdot (e^{2 x} \sin (x)) - \frac{\cos (x) e^{2 x}}{4}) (\frac{4}{5})}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3

Simplify the right side.

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Step 7.2.3.1

Simplify each term.

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Step 7.2.3.1.1

Simplify the numerator.

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Step 7.2.3.1.1.1

Factor $e^{2 x}$ out of $\frac{1}{2} \cdot e^{2 x} \sin (x) - \frac{\cos (x) e^{2 x}}{4}$ .

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Step 7.2.3.1.1.1.1

Factor $e^{2 x}$ out of $\frac{1}{2} \cdot e^{2 x} \sin (x)$ .

$y = \frac{(e^{2 x} (\frac{1}{2} \sin (x)) - \frac{\cos (x) e^{2 x}}{4}) \frac{4}{5}}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.1.1.2

Factor $e^{2 x}$ out of $- \frac{\cos (x) e^{2 x}}{4}$ .

$y = \frac{(e^{2 x} (\frac{1}{2} \sin (x)) + e^{2 x} (- \frac{\cos (x)}{4})) \frac{4}{5}}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.1.1.3

Factor $e^{2 x}$ out of $e^{2 x} (\frac{1}{2} \sin (x)) + e^{2 x} (- \frac{\cos (x)}{4})$ .

$y = \frac{e^{2 x} (\frac{1}{2} \sin (x) - \frac{\cos (x)}{4}) \frac{4}{5}}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.1.2

Combine $\frac{1}{2}$ and $\sin (x)$ .

$y = \frac{e^{2 x} (\frac{\sin (x)}{2} - \frac{\cos (x)}{4}) \frac{4}{5}}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.1.3

Combine $\frac{4}{5}$ and $e^{2 x}$ .

$y = \frac{\frac{4 e^{2 x}}{5} (\frac{\sin (x)}{2} - \frac{\cos (x)}{4})}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.2

Factor $\frac{4 e^{2 x}}{5}$ out of $\frac{\frac{4 e^{2 x}}{5} (\frac{\sin (x)}{2} - \frac{\cos (x)}{4})}{e^{2 x}}$ .

$y = \frac{4 e^{2 x}}{5} \cdot \frac{\frac{\sin (x)}{2} - \frac{\cos (x)}{4}}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.3

Cancel the common factor of $e^{2 x}$ .

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Step 7.2.3.1.3.1

Factor $e^{2 x}$ out of $4 e^{2 x}$ .

$y = \frac{e^{2 x} \cdot 4}{5} \cdot \frac{\frac{\sin (x)}{2} - \frac{\cos (x)}{4}}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.3.2

Cancel the common factor.

$y = \frac{e^{2 x} \cdot 4}{5} \cdot \frac{\frac{\sin (x)}{2} - \frac{\cos (x)}{4}}{e^{2 x}} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.3.3

Rewrite the expression.

$y = \frac{4}{5} (\frac{\sin (x)}{2} - \frac{\cos (x)}{4}) + \frac{C}{e^{2 x}}$

Step 7.2.3.1.4

Apply the distributive property.

$y = \frac{4}{5} \cdot \frac{\sin (x)}{2} + \frac{4}{5} (- \frac{\cos (x)}{4}) + \frac{C}{e^{2 x}}$

Step 7.2.3.1.5

Cancel the common factor of $2$ .

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Step 7.2.3.1.5.1

Factor $2$ out of $4$ .

$y = \frac{2 (2)}{5} \cdot \frac{\sin (x)}{2} + \frac{4}{5} (- \frac{\cos (x)}{4}) + \frac{C}{e^{2 x}}$

Step 7.2.3.1.5.2

Cancel the common factor.

$y = \frac{2 \cdot 2}{5} \cdot \frac{\sin (x)}{2} + \frac{4}{5} (- \frac{\cos (x)}{4}) + \frac{C}{e^{2 x}}$

Step 7.2.3.1.5.3

Rewrite the expression.

$y = \frac{2}{5} \sin (x) + \frac{4}{5} (- \frac{\cos (x)}{4}) + \frac{C}{e^{2 x}}$

Step 7.2.3.1.6

Combine $\frac{2}{5}$ and $\sin (x)$ .

$y = \frac{2 \sin (x)}{5} + \frac{4}{5} (- \frac{\cos (x)}{4}) + \frac{C}{e^{2 x}}$

Step 7.2.3.1.7

Cancel the common factor of $4$ .

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Step 7.2.3.1.7.1

Move the leading negative in $- \frac{\cos (x)}{4}$ into the numerator.

$y = \frac{2 \sin (x)}{5} + \frac{4}{5} \cdot \frac{- \cos (x)}{4} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.7.2

Cancel the common factor.

$y = \frac{2 \sin (x)}{5} + \frac{4}{5} \cdot \frac{- \cos (x)}{4} + \frac{C}{e^{2 x}}$

Step 7.2.3.1.7.3

Rewrite the expression.

$y = \frac{2 \sin (x)}{5} + \frac{1}{5} (- \cos (x)) + \frac{C}{e^{2 x}}$

Step 7.2.3.1.8

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

$y = \frac{2 \sin (x)}{5} - \frac{\cos (x)}{5} + \frac{C}{e^{2 x}}$