$\displaystyle (sin 2x + sin x) / (cos 2x + cos x+1) = tan x$
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Originally Posted by nerdzor $\displaystyle (sin 2x + sin x) / (cos 2x + cos x+1) = tan x$ Substitute the double angle formula into the left hand side: $\displaystyle \sin(2x) = 2 \sin x \cos x$ $\displaystyle \cos (2x) = 2 \cos^2 x - 1$ Simplify. Factorise. Cancel the common factor. Viola!
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