Trigonometrymedium · Past Paper
Express cos 2A in terms of tan A.
A(1 - tan² A) / (1 + tan² A)
B(1 + tan² A) / (1 - tan² A)
C2 tan A / (1 + tan² A)
D1 / (1 + tan² A)
✓ Correct Answer: A — (1 - tan² A) / (1 + tan² A)
This is the identity relating the cosine double angle to tangent.
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