Trigonometryhard · Past Paper
Value of cos(pi/7) cos(2pi/7) cos(4pi/7) is:
A1/8
B-1/8
C1/16
D-1/16
✓ Correct Answer: B — -1/8
Using product of cosines formula: sin(8pi/7) / (8 sin(pi/7)) = -sin(pi/7) / (8 sin(pi/7)) = -1/8.
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