见图
∫sinxcosx/(cosx+sinx) dx=∫sinxcosx(cosx-sinx) /[(cosx+sinx) (cosx-sinx) ]dx=∫sin2x(cosx-sinx) /cos2x]dx=∫tan2x(cosx-sinx) dx看看这样能做不?
∫sinxcosx/(cosx+sinx) dx =-(1/4)∫d(1-2sin^2x)/(1-2sin^2x) = -(1/4)ln(1-2sin^2x)+C