∫(1+cosx^3)dx
=x+∫cosx^3dx
=x+∫(1-sinx^2)dsinx
=x+sinx-(sinx)^3/3+C∫(1+cos3x）sec2xdx我看习题的答案为什么下一步就是∫sec2xdx+∫cosxdx?(1+cosx^3)(secx)^2secx=1/cosx=secx^2+cosx^3/cosx^2=secx^2+cosx∫(1+cosx^3)secx^2dx=∫secx^2dx+∫cosxdx=tanx+sinx+C