Calculus Examples

$\frac{d y}{d x} + y^{2} \sin (x) = 0$

Step 1

Separate the variables.

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Step 1.1

Subtract $y^{2} \sin (x)$ from both sides of the equation.

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

Step 1.2

Multiply both sides by $\frac{1}{y^{2}}$ .

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

Step 1.3

Simplify.

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Step 1.3.1

Rewrite using the commutative property of multiplication.

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

Step 1.3.2

Cancel the common factor of $y^{2}$ .

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Step 1.3.2.1

Move the leading negative in $- \frac{1}{y^{2}}$ into the numerator.

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

Step 1.3.2.2

Factor $y^{2}$ out of $y^{2} \sin (x)$ .

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

Step 1.3.2.3

Cancel the common factor.

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

Step 1.3.2.4

Rewrite the expression.

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

Step 1.4

Rewrite the equation.

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

Step 2

Integrate both sides.

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Step 2.1

Set up an integral on each side.

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

Step 2.2

Integrate the left side.

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Step 2.2.1

Apply basic rules of exponents.

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Step 2.2.1.1

Move $y^{2}$ out of the denominator by raising it to the $- 1$ power.

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

Step 2.2.1.2

Multiply the exponents in ${(y^{2})}^{- 1}$ .

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Step 2.2.1.2.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

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

Step 2.2.1.2.2

Multiply $2$ by $- 1$ .

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

Step 2.2.2

By the Power Rule, the integral of $y^{- 2}$ with respect to $y$ is $- y^{- 1}$ .

$- y^{- 1} + C_{1} = \int - \sin (x) d x$

Step 2.2.3

Rewrite $- y^{- 1} + C_{1}$ as $- \frac{1}{y} + C_{1}$ .

$- \frac{1}{y} + C_{1} = \int - \sin (x) d x$

Step 2.3

Integrate the right side.

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Step 2.3.1

Since $- 1$ is constant with respect to $x$ , move $- 1$ out of the integral.

$- \frac{1}{y} + C_{1} = - \int \sin (x) d x$

Step 2.3.2

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

$- \frac{1}{y} + C_{1} = - (- \cos (x) + C_{2})$

Step 2.3.3

Simplify the answer.

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Step 2.3.3.1

Simplify.

$- \frac{1}{y} + C_{1} = - - \cos (x) + C_{2}$

Step 2.3.3.2

Simplify.

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Step 2.3.3.2.1

Multiply $- 1$ by $- 1$ .

$- \frac{1}{y} + C_{1} = 1 \cos (x) + C_{2}$

Step 2.3.3.2.2

Multiply $\cos (x)$ by $1$ .

$- \frac{1}{y} + C_{1} = \cos (x) + C_{2}$

Step 2.4

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

$- \frac{1}{y} = \cos (x) + K$

Step 3

Solve for $y$ .

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Step 3.1

Find the LCD of the terms in the equation.

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Step 3.1.1

Finding the LCD of a list of values is the same as finding the LCM of the denominators of those values.

$y, 1, 1$

Step 3.1.2

The LCM of one and any expression is the expression.

$y$

Step 3.2

Multiply each term in $- \frac{1}{y} = \cos (x) + K$ by $y$ to eliminate the fractions.

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Step 3.2.1

Multiply each term in $- \frac{1}{y} = \cos (x) + K$ by $y$ .

$- \frac{1}{y} y = \cos (x) y + K y$

Step 3.2.2

Simplify the left side.

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Step 3.2.2.1

Cancel the common factor of $y$ .

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Step 3.2.2.1.1

Move the leading negative in $- \frac{1}{y}$ into the numerator.

$\frac{- 1}{y} y = \cos (x) y + K y$

Step 3.2.2.1.2

Cancel the common factor.

$\frac{- 1}{y} y = \cos (x) y + K y$

Step 3.2.2.1.3

Rewrite the expression.

$- 1 = \cos (x) y + K y$

Step 3.2.3

Simplify the right side.

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Step 3.2.3.1

Reorder factors in $\cos (x) y + K y$ .

$- 1 = y \cos (x) + K y$

Step 3.3

Solve the equation.

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Step 3.3.1

Rewrite the equation as $y \cos (x) + K y = - 1$ .

$y \cos (x) + K y = - 1$

Step 3.3.2

Factor $y$ out of $y \cos (x) + K y$ .

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Step 3.3.2.1

Factor $y$ out of $y \cos (x)$ .

$y (\cos (x)) + K y = - 1$

Step 3.3.2.2

Factor $y$ out of $K y$ .

$y (\cos (x)) + y K = - 1$

Step 3.3.2.3

Factor $y$ out of $y (\cos (x)) + y K$ .

$y (\cos (x) + K) = - 1$

Step 3.3.3

Divide each term in $y (\cos (x) + K) = - 1$ by $\cos (x) + K$ and simplify.

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Step 3.3.3.1

Divide each term in $y (\cos (x) + K) = - 1$ by $\cos (x) + K$ .

$\frac{y (\cos (x) + K)}{\cos (x) + K} = \frac{- 1}{\cos (x) + K}$

Step 3.3.3.2

Simplify the left side.

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Step 3.3.3.2.1

Cancel the common factor of $\cos (x) + K$ .

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Step 3.3.3.2.1.1

Cancel the common factor.

$\frac{y (\cos (x) + K)}{\cos (x) + K} = \frac{- 1}{\cos (x) + K}$

Step 3.3.3.2.1.2

Divide $y$ by $1$ .

$y = \frac{- 1}{\cos (x) + K}$

Step 3.3.3.3

Simplify the right side.

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Step 3.3.3.3.1

Move the negative in front of the fraction.

$y = - \frac{1}{\cos (x) + K}$