Trigonometry Examples

$\sin (x) \cdot \cos (x) = \frac{1}{2}$

Step 1

Multiply each term in $\sin (x) \cdot \cos (x) = \frac{1}{2}$ by $2$ to eliminate the fractions.

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Multiply each term in $\sin (x) \cdot \cos (x) = \frac{1}{2}$ by $2$ .

$\sin (x) \cdot \cos (x) \cdot 2 = \frac{1}{2} \cdot 2$

Simplify the left side.

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Reorder $\sin (x) \cdot \cos (x)$ and $2$ .

$2 \cdot (\sin (x) \cdot \cos (x)) = \frac{1}{2} \cdot 2$

Apply the sine double-angle identity.

$\sin (2 x) = \frac{1}{2} \cdot 2$

Simplify the right side.

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Cancel the common factor of $2$ .

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Cancel the common factor.

$\sin (2 x) = \frac{1}{2} \cdot 2$

Rewrite the expression.

$\sin (2 x) = 1$

Step 2

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

$2 x = \arcsin (1)$

Step 3

Simplify the right side.

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The exact value of $\arcsin (1)$ is $\frac{π}{2}$ .

$2 x = \frac{π}{2}$

Step 4

Divide each term in $2 x = \frac{π}{2}$ by $2$ and simplify.

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Divide each term in $2 x = \frac{π}{2}$ by $2$ .

$\frac{2 x}{2} = \frac{\frac{π}{2}}{2}$

Simplify the left side.

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Cancel the common factor of $2$ .

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Cancel the common factor.

$\frac{2 x}{2} = \frac{\frac{π}{2}}{2}$

Divide $x$ by $1$ .

$x = \frac{\frac{π}{2}}{2}$

Simplify the right side.

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Multiply the numerator by the reciprocal of the denominator.

$x = \frac{π}{2} \cdot \frac{1}{2}$

Multiply $\frac{π}{2} \cdot \frac{1}{2}$ .

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

$x = \frac{π}{2 \cdot 2}$

Multiply $2$ by $2$ .

$x = \frac{π}{4}$

Step 5

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.

$2 x = π - \frac{π}{2}$

Step 6

Solve for $x$ .

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Simplify.

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To write $π$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$2 x = π \cdot \frac{2}{2} - \frac{π}{2}$

Combine $π$ and $\frac{2}{2}$ .

$2 x = \frac{π \cdot 2}{2} - \frac{π}{2}$

Combine the numerators over the common denominator.

$2 x = \frac{π \cdot 2 - π}{2}$

Subtract $π$ from $π \cdot 2$ .

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Reorder $π$ and $2$ .

$2 x = \frac{2 \cdot π - π}{2}$

Subtract $π$ from $2 \cdot π$ .

$2 x = \frac{π}{2}$

Divide each term in $2 x = \frac{π}{2}$ by $2$ and simplify.

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Divide each term in $2 x = \frac{π}{2}$ by $2$ .

$\frac{2 x}{2} = \frac{\frac{π}{2}}{2}$

Simplify the left side.

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Cancel the common factor of $2$ .

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Cancel the common factor.

$\frac{2 x}{2} = \frac{\frac{π}{2}}{2}$

Divide $x$ by $1$ .

$x = \frac{\frac{π}{2}}{2}$

Simplify the right side.

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Multiply the numerator by the reciprocal of the denominator.

$x = \frac{π}{2} \cdot \frac{1}{2}$

Multiply $\frac{π}{2} \cdot \frac{1}{2}$ .

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

$x = \frac{π}{2 \cdot 2}$

Multiply $2$ by $2$ .

$x = \frac{π}{4}$

Step 7

Find the period of $\sin (2 x)$ .

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

$\frac{2 π}{| b |}$

Replace $b$ with $2$ in the formula for period.

$\frac{2 π}{| 2 |}$

The absolute value is the distance between a number and zero. The distance between $0$ and $2$ is $2$ .

$\frac{2 π}{2}$

Cancel the common factor of $2$ .

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Cancel the common factor.

$\frac{2 π}{2}$

Divide $π$ by $1$ .

$π$

Step 8

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

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