I=∫sin x logcos x dxPut cos x=t⇒−sin x dx=dt⇒I=−∫logt dt
Using integration by parts,
∫uv dx=u∫v dx−∫dudx (∫v dx) dx
Here, u and v according to ILATE rule are log t and 1 respectively.
∴I=−tloget+∫t⋅1t dt=−tloget+t+C
=t(1−loget)+C=cos x(1−logecos x)+C