Precalculus Examples

$\sin (3 x) = \frac{\sqrt{2}}{2}$

Step 1

Take the inverse sine of both sides of the equation to extract $x$ from inside the sine.

$3 x = \arcsin (\frac{\sqrt{2}}{2})$

Step 2

Simplify the right side.

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Step 2.1

The exact value of $\arcsin (\frac{\sqrt{2}}{2})$ is $\frac{π}{4}$ .

$3 x = \frac{π}{4}$

Step 3

Divide each term in $3 x = \frac{π}{4}$ by $3$ and simplify.

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Step 3.1

Divide each term in $3 x = \frac{π}{4}$ by $3$ .

$\frac{3 x}{3} = \frac{\frac{π}{4}}{3}$

Step 3.2

Simplify the left side.

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Step 3.2.1

Cancel the common factor of $3$ .

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Step 3.2.1.1

Cancel the common factor.

$\frac{3 x}{3} = \frac{\frac{π}{4}}{3}$

Step 3.2.1.2

Divide $x$ by $1$ .

$x = \frac{\frac{π}{4}}{3}$

Step 3.3

Simplify the right side.

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Step 3.3.1

Multiply the numerator by the reciprocal of the denominator.

$x = \frac{π}{4} \cdot \frac{1}{3}$

Step 3.3.2

Multiply $\frac{π}{4} \cdot \frac{1}{3}$ .

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Step 3.3.2.1

Multiply $\frac{π}{4}$ by $\frac{1}{3}$ .

$x = \frac{π}{4 \cdot 3}$

Step 3.3.2.2

Multiply $4$ by $3$ .

$x = \frac{π}{12}$

Step 4

The sine function is positive in the first and second quadrants. To find the second solution, subtract the reference angle from $π$ to find the solution in the second quadrant.

$3 x = π - \frac{π}{4}$

Step 5

Solve for $x$ .

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Step 5.1

Simplify.

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Step 5.1.1

To write $π$ as a fraction with a common denominator, multiply by $\frac{4}{4}$ .

$3 x = π \cdot \frac{4}{4} - \frac{π}{4}$

Step 5.1.2

Combine $π$ and $\frac{4}{4}$ .

$3 x = \frac{π \cdot 4}{4} - \frac{π}{4}$

Step 5.1.3

Combine the numerators over the common denominator.

$3 x = \frac{π \cdot 4 - π}{4}$

Step 5.1.4

Subtract $π$ from $π \cdot 4$ .

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Step 5.1.4.1

Reorder $π$ and $4$ .

$3 x = \frac{4 \cdot π - π}{4}$

Step 5.1.4.2

Subtract $π$ from $4 \cdot π$ .

$3 x = \frac{3 \cdot π}{4}$

Step 5.2

Divide each term in $3 x = \frac{3 \cdot π}{4}$ by $3$ and simplify.

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Step 5.2.1

Divide each term in $3 x = \frac{3 \cdot π}{4}$ by $3$ .

$\frac{3 x}{3} = \frac{\frac{3 \cdot π}{4}}{3}$

Step 5.2.2

Simplify the left side.

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Step 5.2.2.1

Cancel the common factor of $3$ .

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Step 5.2.2.1.1

Cancel the common factor.

$\frac{3 x}{3} = \frac{\frac{3 \cdot π}{4}}{3}$

Step 5.2.2.1.2

Divide $x$ by $1$ .

$x = \frac{\frac{3 \cdot π}{4}}{3}$

Step 5.2.3

Simplify the right side.

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Step 5.2.3.1

Multiply the numerator by the reciprocal of the denominator.

$x = \frac{3 \cdot π}{4} \cdot \frac{1}{3}$

Step 5.2.3.2

Cancel the common factor of $3$ .

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Step 5.2.3.2.1

Factor $3$ out of $3 \cdot π$ .

$x = \frac{3 (π)}{4} \cdot \frac{1}{3}$

Step 5.2.3.2.2

Cancel the common factor.

$x = \frac{3 π}{4} \cdot \frac{1}{3}$

Step 5.2.3.2.3

Rewrite the expression.

$x = \frac{π}{4}$

Step 6

Find the period of $\sin (3 x)$ .

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Step 6.1

The period of the function can be calculated using $\frac{2 π}{| b |}$ .

$\frac{2 π}{| b |}$

Step 6.2

Replace $b$ with $3$ in the formula for period.

$\frac{2 π}{| 3 |}$

Step 6.3

The absolute value is the distance between a number and zero. The distance between $0$ and $3$ is $3$ .

$\frac{2 π}{3}$

Step 7

The period of the $\sin (3 x)$ function is $\frac{2 π}{3}$ so values will repeat every $\frac{2 π}{3}$ radians in both directions.

$x = \frac{π}{12} + \frac{2 π n}{3}, \frac{π}{4} + \frac{2 π n}{3}$ , for any integer $n$