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

question 199

Multiple Choice

Use the Half-angle Formulas to find the exact value of the trigonometric function.
- $\cos 22.5 ^ { \circ }$

• A) \(\frac { 1 } { 2 } \sqrt { 2 - \sqrt { 2 } }\)
• B) \(- \frac { 1 } { 2 } \sqrt { 2 - \sqrt { 2 } }\)
• C) \(- \frac { 1 } { 2 } \sqrt { 2 + \sqrt { 2 } }\)
• D) \(\frac { 1 } { 2 } \sqrt { 2 + \sqrt { 2 } }\)

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