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Question

Mathematics Question on Trigonometric Functions

The value of cos⁡π15 cos⁡2π15 cos⁡4π15 cos⁡8π15\cos \frac{\pi}{15}\, \cos \frac{2\pi}{15}\, \cos \frac{4\pi}{15}\, \cos \frac{8\pi}{15} is

A

116\frac{1}{16}

B

−116-\frac{1}{16}

C

11

D

00

Answer

−116-\frac{1}{16}

Explanation

Solution

cos⁡π15⋅cos⁡2π15⋅cos⁡4π15⋅cos⁡8π15\cos \frac{\pi}{15} \cdot \cos \frac{2\pi}{15} \cdot \cos \frac{4\pi}{15} \cdot \cos \frac{8\pi}{15}