Math CentralQuandaries & Queries


Question from Joe, a student:

I really need help with this question and I would really appreciate if you could take a minute and look at it.

Prove this Trig. Identity :

((cos2θ + sinθ-1) / tanθ ) + sin2θ = cosθ

Thank you

Hi Joe,

I would first multiply both sides of

\[\frac{\cos 2\theta + \sin \theta -1}{\tan \theta} + \sin 2 \theta = \cos \theta\]

by $\tan \theta.$ Next write $\cos 2 \theta, \sin 2 \theta \mbox{ and } \tan \theta$ in terms of $\sin \theta$ and $\cos \theta$ and then simplify.

I hope this helps,

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