∫ cos(ln x) dx= ∫ xcos(ln x) d(ln x)= ∫ x d(sin(ln x))= xsin(ln x) - ∫ sin(ln x) dx= xsin(ln x) - ∫ xsin(ln x) d(ln x)= xsin(ln x) + ∫ x d(cos(ln x))= xsin(ln x) + xcos(ln x) - ∫ cos(ln x) dx2...