cos 10 . cos 50 . cos 70 = √3/8
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Answer:
To prove:
cos 10° cos 50° cos 70°=√3/8
LHS,
cos 10° cos 50° cos 70°=
cos(60-Q) cosQ cos(60+Q)
where, Q=10 such that
cos(60-Q) cosQ cos(60+Q)=
1/4(cos 3Q
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