(2)=-1/4∫xdcos4x=-xcos4x/4+sin4x/16+C(3)=-∫lnxd(1/x)=-lnx/x+∫1/x²dx=-lnx/x-1/x+C(4)=xarcsinx-∫x/√(1-x²)dx=xarcsinx+1/2∫(1-x²)^(-1/2)d(1-x²)=xarcsinx+√(1-x²)+C
