(c) We note that
dxd(xtanx+1)=xsec2x+tanx∴ integrating by parts with
x2 as first function, we get
I=∫x2(xtanx+1)2xsec2x+tanxdx=x2(−xtanx+11)−∫2x(−xtanx+11)dx=−xtanx+1x2+2∫xsinx+cosxxcosxdx=−xtanx+1x2+2loge∣xsinx+cosx∣+c(∵dxd(xsinx+cosx)=xcosx)