cos pie/5 * cos 2pie/5 * cos 4pie/5 * cos8pie/5
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Answer:
Cos ( π / 5 ) cos ( 2 π / 5 ) cos ( 4 π / 5 ) cos ( 8 π / 5 ) .
= 1/2⁴ sin ( π /5 ) sin 2⁴π / 5 .
= 1/-16 [ Sin 16 π / 5
= sin ( 3π + π 5 )
= - sin. π / 5 ]
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