Find the exact value of the expression.
-cos (-390°)
A) $\frac { 1 } { 2 }$
B) $\frac { \sqrt { 3 } } { 2 }$
C) $- \frac { \sqrt { 3 } } { 2 }$
D) $- \frac { 1 } { 2 }$

Name: Find the exact value of the expression. -cos (-390°) A) $\frac { 1 } { 2 }$ B) $\frac { \sqrt { 3 } } { 2 }$ C) $- \frac { \sqrt { 3 } } { 2 }$ D) $- \frac { 1 } { 2 }$
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Question

Find the exact value of the expression.
-cos (-390°) 
A) $\frac { 1 } { 2 }$
B) $\frac { \sqrt { 3 } } { 2 }$
C) $- \frac { \sqrt { 3 } } { 2 }$
D) $- \frac { 1 } { 2 }$

Quizplus · Accepted Answer

The angle -390° is coterminal with -390° + 360° = -30°, and cos(-30°) = cos(30°) = $\frac{\sqrt{3}}{2}$.

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