∫x/(cosx)^2 dx
问题描述:
∫x/(cosx)^2 dx
求这道题的是多少?
答
=∫x(secx)^2dx
=∫xdtanx
=xtanx-∫tanxdx
=xtanx-∫sinx/cosxdx
=xtanx+∫dcosx/cosx
=xtanx+ln|cosx|+C