Trigonometryhard · Past Paper
Simplify: 2 cos(π/4 + A) cos(π/4 - A).
Acos 2A
Bsin 2A
Ccos² A
Dsin² A
✓ Correct Answer: A — cos 2A
Using 2 cos X cos Y = cos(X+Y) + cos(X-Y): cos(π/2) + cos(2A) = 0 + cos 2A = cos 2A.
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✓ Correct Answer: A — cos 2A
Using 2 cos X cos Y = cos(X+Y) + cos(X-Y): cos(π/2) + cos(2A) = 0 + cos 2A = cos 2A.
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