Use the even-odd properties to find the exact value of the expression. Do not use a calculator.
-$\cos \left( - 60 ^ { \circ } \right)$
A) $\frac { 1 } { 2 }$
B) $- \frac { \sqrt { 3 } } { 2 }$
C) $\frac { \sqrt { 3 } } { 2 }$
D) $- \frac { 1 } { 2 }$

Question

Quizplus · Accepted Answer

Cosine is an even function, meaning $\cos(-\theta) = \cos(\theta)$. Therefore, $\cos(-60^\circ) = \cos(60^\circ) = \frac{1}{2}$.

Use the Even-Odd Properties to Find the Exact Value of the Expression