已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x
问题描述：
已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x
答
sinx=2cosx , sin^2x=4cos^2x
sin^2x=4-4sin^2x ,sin^2x=4/5
(cos x+sin x)/(cos x-sin x)+sin^2x
=(1+tanx)/(1-tanx)+sin^2x
=-3+4/5=-11/5