Find the exact value by using a half-angle identity.
-$\cos \frac { 5 \pi } { 12 }$
A) $- \frac { 1 } { 2 } \sqrt { 2 + \sqrt { 3 } }$
B) $\frac { 1 } { 2 } \sqrt { 2 + \sqrt { 3 } }$
C) $\frac { 1 } { 2 } \sqrt { 2 - \sqrt { 3 } }$
D) $- \frac { 1 } { 2 } \sqrt { 2 - \sqrt { 3 } }$

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The Answer of Find the exact value by using a half-angle identity.
-$\cos \frac { 5 \pi } { 12 }$
A) $- \frac { 1 } { 2 } \sqrt { 2 + \sqrt { 3 } }$
B) $\frac { 1 } { 2 } \sqrt { 2 + \sqrt { 3 } }$
C) $\frac { 1 } { 2 } \sqrt { 2 - \sqrt { 3 } }$
D) $- \frac { 1 } { 2 } \sqrt { 2 - \sqrt { 3 } }$

Find the Exact Value by Using a Half-Angle Identity cos⁡5π12\cos \frac { 5 \pi } { 12 }cos125π​

Find the Exact Value by Using a Half-Angle Identity $\cos \frac { 5 \pi } { 12 }$