A) 1/2
B) 1/4
C) 1/8
D) 1/16
Correct Answer: D
Solution :
\[\cos \frac{2\pi }{15}\cos \frac{4\pi }{15}\cos \frac{8\pi }{15}\cos \frac{16\pi }{15}\] \[=\frac{\sin \,{{2}^{4}}\frac{2\pi }{15}}{{{2}^{4}}\sin \frac{2\pi }{15}}=\frac{\sin \,\frac{32\pi }{15}}{16\,\sin \frac{2\pi }{15}}=\frac{1}{16}\frac{\sin \frac{2\pi }{15}}{\sin \frac{2\pi }{15}}=\frac{1}{16}\].
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