alleryStart learning →Using cos²θ = (1 + cos 2θ)/2, find cos²15°.
A(2 − √3)/4
B(2 + √3)/2
C(1 + √3)/4
D(2 + √3)/4
Answer & Solution
Correct answer: D. (2 + √3)/4
cos²15° = (1 + cos 30°)/2 = (1 + √3/2)/2 = (2 + √3)/4.
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