Use the Half-Angle Formulas to Find the Exact Value of the Trigonometric

question 18

Multiple Choice

Use the Half-angle Formulas to find the exact value of the trigonometric function.
- $\cos 165 ^ { \circ }$

• 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) \(- \frac { 1 } { 2 } \sqrt { 2 - \sqrt { 3 } }\)