Find the exact value of the expression.
-$\cos 2040 ^ { \circ }$
A) $\frac { \sqrt { 2 } } { 2 }$
B) $- \sqrt { 3 }$
C) $- \frac { \sqrt { 3 } } { 2 }$
D) $- \frac { 1 } { 2 }$

Question

Quizplus · Accepted Answer

The angle 2040° is coterminal with 60° (since 2040° - 5*360° = 60°). The cosine of 60° is $\frac{1}{2}$, so the cosine of 2040° is also $\frac{1}{2}$. However, since 2040° is in the third quadrant where cosine is negative, the value is $-\frac{1}{2}$.

Find the Exact Value of the Expression cos⁡2040∘\cos 2040 ^ { \circ }cos2040∘

Find the Exact Value of the Expression $\cos 2040 ^ { \circ }$