The double angle formula sin 2A equals:
A$\sin A + \cos A$ (incorrect sum)
B$2 \sin A \cos A$ (the correct formula)
C$\sin^2 A - \cos^2 A$ (resembles cos 2A)
D$2 \sin^2 A$ (only partial)
Answer & Solution
Correct answer: B. $2 \sin A \cos A$ (the correct formula)
sin 2A = 2 sin A cos A. Comes from sin(A+A) = sin A cos A + cos A sin A. cos 2A has multiple equivalent forms: cos²A − sin²A = 2cos²A − 1 = 1 − 2sin²A.
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