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Prove that : sin9°. sin27°. sin63°. sin81° = cos9°.cos27°.cos63°.cos81°

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Prove that : sin9°. sin27°. sin63°. sin81° = cos9°.cos27°.cos63°.cos81°

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Taking LHS

= sin 9° sin 27° sin 63° sin 81°

= cos (90° - 9°) cos (90° - 27°) cos (90° – 63°) cos (90°- 81°)

= cos 81° cos 63° cos 27° cos 9°

Or cos 9° cos 27° cos 63° cos 81° = RHS

Hence Proved

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