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anonymous
 5 years ago
Prove the identity
(cos 3x+cos x)/(sin3xsinx)=cotx
anonymous
 5 years ago
Prove the identity (cos 3x+cos x)/(sin3xsinx)=cotx

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Mertsj
 5 years ago
Best ResponseYou've already chosen the best response.1\[\cos x+\cos y=2\cos \frac{x+y}{2}\cos \frac{xy}{2}\]

Mertsj
 5 years ago
Best ResponseYou've already chosen the best response.1So cos 3x+cosx=2cos2xcosx Also: \[\sin x+\sin y=2\cos \frac{x+y}{2}\cos \frac{xy}{2}\]

Mertsj
 5 years ago
Best ResponseYou've already chosen the best response.1So sin3xsinx = 2cos2xsinx

Mertsj
 5 years ago
Best ResponseYou've already chosen the best response.1So \[\frac{\cos 3x+\cos x}{\sin 3x\sin x}=\frac{2\cos 2x \cos x}{2\cos 2x \sin x}=\frac{\cos x}{\sin x}=\cot x\]

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0\[\sin x+\sin y=2\sin \frac{x+y}{2}\cos \frac{xy}{2} ****\]
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