I=intx/(1+sinx)dx=int(x(1-sinx))/(1-sin^2x)dx=int(x(1-sinx))/cos^2xdx =>I=intxsec^2xdx-intxsecxtanxdx Integration by parts,we get I=[xtanx-int1*tanxdx]-[x*secx-int1*secxdx] I=xtanx-ln|secx|-xsecx+ln|secx+tanx|+c =xtanx-xsecx+ln|secx+tanx|-ln|secx|+c =x(tanx-secx)+ln|(secx+tanx)/secx|+c