Integrate x tanx.
Given ∫xtanxdx
Using the rule of ∫uvdx=u∫vdx−∫[u′∫vdx]dx
Now, replace u=x and v=tanx, we get
⇒∫xtanxdx=x∫tanxdx−∫[(x)′∫tanxdx]dx
=xlncosx+∫lncosxdx [Since, ∫tanx=−lncosx+c]
∴∫xtanxdx=xln|cosx|+cosxln|cosx|−cosx+c [Since ∫ln|x|=xlnx−x+c]