∫cos2x/[(sinx)^2(cosx)^2]dx=1/2∫dsin2x/[(sinx)^2(cosx)^2]=1/2∫dsin2x/[1/4(sin2x)^2]=2∫dsin2x/(sin2x)^2=-2/sin2x这个方法应该叫凑微分~不懂就追问哈~
