Solved: "Evaluate the trigonometric function using its period as..."

dammeym

Open question

2022-08-20

Evaluate the trigonometric function using its period as an aid.

\cos (- 13 \frac{π}{3})

Nathalie Foster

Beginner2022-08-21Added 7 answers

To evaluate

\cos (- \frac{13 π}{3})

, we need to find the coterminal angle of

- \frac{13 π}{3}

that lies in the angle

0 \leq 0 < 2 π

. T o find the coterminal angle, we can add a multiple of

2 π

- \frac{13 π}{3} + 3 (2 π) = - \frac{13 π}{3} + 6 π = \frac{5 π}{3}

Therefore:

\cos (- \frac{13 π}{3}) = \cos (\frac{5 π}{3}) = \frac{1}{2}

Result:

\frac{1}{2}

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