S.D.Prove that cos 10 cos 50 cos 70° =3/8 – InterviewSolution

1.

S.D.Prove that cos 10 cos 50 cos 70° =3/8

Answer»

To prove:cos 10° cos 50° cos 70°=√3/8LHS,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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