Use a calculator to evaluate the trigonometric function. Round your answer to four decimal places. (Be sure the calculator is set to the correct angle mode.)
$\sec \left( \frac { - 5 \pi } { 8 } \right)$
A) $1.0006$
B) $- 1.0824$
C) $1.2331$
D) $- 2.6131$
E) $0.4142$

Question

Quizplus · Accepted Answer

The secant function is the reciprocal of the cosine function. To find $\sec \left( \frac { - 5 \pi } { 8 } \right)$, first find $\cos \left( \frac { - 5 \pi } { 8 } \right)$ and then take its reciprocal. Using a calculator set to radian mode, the cosine value is approximately -0.3827. Taking the reciprocal gives $- 2.6131$, which matches choice D.

Use a Calculator to Evaluate the Trigonometric Function sec⁡(−5π8)\sec \left( \frac { - 5 \pi } { 8 } \right)sec(8−5π​)

Use a Calculator to Evaluate the Trigonometric Function $\sec \left( \frac { - 5 \pi } { 8 } \right)$