∫x/(cosx)^2 dx

问题描述:

∫x/(cosx)^2 dx
求这道题的是多少?

=∫x(secx)^2dx
=∫xdtanx
=xtanx-∫tanxdx
=xtanx-∫sinx/cosxdx
=xtanx+∫dcosx/cosx
=xtanx+ln|cosx|+C