Trigonometryhard · Past Paper
In ABC, cot A/2 + cot B/2 + cot C/2 = ?
Acot A/2 cot B/2 cot C/2
B1
C0
Dtan A/2 tan B/2 tan C/2
✓ Correct Answer: A — cot A/2 cot B/2 cot C/2
This is a conditional identity for half-angles of a triangle.
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