Evaluate the trigonometric function.Round your answer to four decimal places.(Be sure the calculator is set in the correct angle mode. ) $\cos ( - 1180 )$
A)-0.1736
B)0.3264
C)-0.0736
D)0.1264
E)0.2264

Question

Evaluate the trigonometric function.Round your answer to four decimal places.(Be sure the calculator is set in the correct angle mode. )​ $\cos ( - 1180 )$ ​
A)-0.1736
B)0.3264
C)-0.0736
D)0.1264
E)0.2264

Quizplus · Accepted Answer

The cosine function has a period of $360^\circ$, so $\cos(-1180^\circ)$ is equivalent to $\cos(-1180^\circ + 360^\circ \times 4)$, which simplifies to $\cos(200^\circ)$. Since $\cos(200^\circ)$ is in the third quadrant where cosine is negative, and its reference angle is $20^\circ$, the value is close to $\cos(180^\circ - 20^\circ) = -\cos(20^\circ)$, which rounds to approximately -0.1736.

Evaluate the Trigonometric Function cos⁡(−1180)\cos ( - 1180 )cos(−1180) ​ A)-0

Evaluate the Trigonometric Function $\cos ( - 1180 )$
A)-0