Trigonometrymedium · Past Paper
What is cos(A+B)cos(A-B)?
Acos^2 A - sin^2 B
Bcos^2 A + sin^2 B
Csin^2 A - cos^2 B
D1
✓ Correct Answer: A — cos^2 A - sin^2 B
This is a product-to-difference identity: cos^2 A - sin^2 B or cos^2 B - sin^2 A.
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