Tuesday 14 May 2013

trigonometry - $sin 2x - tan 2x = -sin 2xtan 2x$ trigonometric identity proof

I need to prove




$$\sin 2x - \tan 2x = -\sin 2x\tan 2x$$





I tried simplifying
$$
\sin 2x = 2\sin x\cos x;\quad \tan 2x = \frac{2\tan x}{1-\tan^2x}.
$$



But it's so long and complicated that I feel I must've made a colossal mistake somewhere, or I am not using the correct equivalence. Or maybe I made a huge oversight from the beginning, and I don't need to simplify them in the first place.



Either way, i am stuck. Please help. Thanks.

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