Prove that sin x + sin 3x + sin 5x + sin 7x =4cos x .cos 2x . sin 4x
Gurvir Kaur Bajwa , 6 Years ago
Grade 11
Trigonometry> Prove that sin x + sin 3x + sin 5x + sin ...
1 Answers
Shashank Singh
Last Activity: 6 Years ago
use sinC +sinD seperately for sinx+sin7x and sin3x +sin5x
we will get,
2sin4xcos3x+2sin4xcosx
= 2sin4x(cos3x+cosx)
= 2sin4x(2cos2xcosx)
= 4cosxcos2xsin4x...... [ans]
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