Trigonometryhard · Past Paper
If tan(A/2) = t, then cos A = ?
A(1-t^2)/(1+t^2)
B2t/(1+t^2)
C2t/(1-t^2)
D(1+t^2)/(1-t^2)
✓ Correct Answer: A — (1-t^2)/(1+t^2)
Cosine formula in terms of half-angle tangent.
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