你对了,答案错了
∫cos^4x=∫cos^3xdsinx=sinxcos^3x-∫sinx*3cos^2x(-sinx)dx
=sinxcos^3x+3∫sin^2cos^2xdx
=sinxcos^3x+3∫(1-cos^2x)cos^2xdx
=sinxcos^3x+3x-3∫cos^4xdx
因此
∫cos^4x=(1/4)sinxcos^3x+3x/4+C
你对了,答案错了
∫cos^4x=∫cos^3xdsinx=sinxcos^3x-∫sinx*3cos^2x(-sinx)dx
=sinxcos^3x+3∫sin^2cos^2xdx
=sinxcos^3x+3∫(1-cos^2x)cos^2xdx
=sinxcos^3x+3x-3∫cos^4xdx
因此
∫cos^4x=(1/4)sinxcos^3x+3x/4+C