Trigonometryhard · Past Paper
Value of cos 36° is:
A(√5 + 1) / 4
B(√5 - 1) / 4
C√(10 + 2√5) / 4
D1/2
✓ Correct Answer: A — (√5 + 1) / 4
In a regular pentagon context or via triple angle formulas, cos 36° = (√5 + 1) / 4.
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