(cotx)^4=[1+cos(2x)]^2/[1-cos(2x)]^2,令θ=2x,再令y=(1+cosθ)/(1-cosθ),即θ=arccos[(y-1)/(y+1)],最后p=√y即可,还原代换算得结果鉴于手机提问只能输100个字最后∫(cotx)^4dx=-(1/3)(cotx)^3+cotx+x+C...