cos(2θ) equals:
AAll of the above
B2 cos²θ - 1
C1 - 2 sin²θ
Dcos²θ - sin²θ
Answer & Solution
Correct answer: A. All of the above
cos(2θ) = cos²θ - sin²θ. Using sin² + cos² = 1, we can rewrite: = 1 - 2sin²θ = 2cos²θ - 1. All three forms are equivalent — useful in different problems.
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