Trigonometry Examples

sec (x) = - 2

$\sec (x) = - 2$

Step 1

Take the inverse secant of both sides of the equation to extract

x

$x$ from inside the secant.

x = arcsec (- 2)

$x = arcsec (- 2)$

Step 2

Simplify the right side.

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Step 2.1

The exact value of

arcsec (- 2)

$arcsec (- 2)$ is

\frac{2 π}{3}

$\frac{2 π}{3}$ .

x = \frac{2 π}{3}

$x = \frac{2 π}{3}$

x = \frac{2 π}{3}

$x = \frac{2 π}{3}$

Step 3

The secant function is negative in the second and third quadrants. To find the second solution, subtract the reference angle from

2 π

$2 π$ to find the solution in the third quadrant.

x = 2 π - \frac{2 π}{3}

$x = 2 π - \frac{2 π}{3}$

Step 4

Simplify

2 π - \frac{2 π}{3}

$2 π - \frac{2 π}{3}$ .

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Step 4.1

To write

2 π

$2 π$ as a fraction with a common denominator, multiply by

\frac{3}{3}

$\frac{3}{3}$ .

x = 2 π \cdot \frac{3}{3} - \frac{2 π}{3}

$x = 2 π \cdot \frac{3}{3} - \frac{2 π}{3}$

Step 4.2

Combine fractions.

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Step 4.2.1

Combine

2 π

$2 π$ and

\frac{3}{3}

$\frac{3}{3}$ .

x = \frac{2 π \cdot 3}{3} - \frac{2 π}{3}

$x = \frac{2 π \cdot 3}{3} - \frac{2 π}{3}$

Step 4.2.2

Combine the numerators over the common denominator.

x = \frac{2 π \cdot 3 - 2 π}{3}

$x = \frac{2 π \cdot 3 - 2 π}{3}$

x = \frac{2 π \cdot 3 - 2 π}{3}

$x = \frac{2 π \cdot 3 - 2 π}{3}$

Step 4.3

Simplify the numerator.

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Step 4.3.1

Multiply

3

$3$ by

2

$2$ .

x = \frac{6 π - 2 π}{3}

$x = \frac{6 π - 2 π}{3}$

Step 4.3.2

Subtract

2 π

$2 π$ from

6 π

$6 π$ .

x = \frac{4 π}{3}

$x = \frac{4 π}{3}$

x = \frac{4 π}{3}

$x = \frac{4 π}{3}$

x = \frac{4 π}{3}

$x = \frac{4 π}{3}$

Step 5

Find the period of

sec (x)

$\sec (x)$ .

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Step 5.1

The period of the function can be calculated using

\frac{2 π}{| b |}

$\frac{2 π}{| b |}$ .

\frac{2 π}{| b |}

$\frac{2 π}{| b |}$

Step 5.2

Replace

b

$b$ with

1

$1$ in the formula for period.

\frac{2 π}{| 1 |}

$\frac{2 π}{| 1 |}$

Step 5.3

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

0

$0$ and

1

$1$ is

1

$1$ .

\frac{2 π}{1}

$\frac{2 π}{1}$

Step 5.4

Divide

2 π

$2 π$ by

1

$1$ .

2 π

$2 π$

2 π

$2 π$

Step 6

The period of the

sec (x)

$\sec (x)$ function is

2 π

$2 π$ so values will repeat every

2 π

$2 π$ radians in both directions.

x = \frac{2 π}{3} + 2 π n, \frac{4 π}{3} + 2 π n

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

n

$n$