设tan(x/2)=t 则sin x=2t/(1+t^2) cos x=(1-t^2)/(1+t^2) dx=2/(1+t^2)dt∫sinx/(sinx+cosx)dx=∫2t/(1+t^2)*2/(1+t^2)/[2t/(1+t^2) +(1-t^2)/(1+t^2)]dt=-4∫t/[(1+t^2)(t+√2-1)(t-√2-1)dt设：t/[(1+t^2)(t+√2-1...