Integration by parts: Let a<ba<b and let u,v:[a,b]Ru,v:[a,b]\to\mathbb{R} be functions that are on [a,b][a,b], with uu' and vv' on [a,b][a,b]. Then

abu(x)v(x)dx=u(b)v(b)u(a)v(a)abu(x)v(x)dx.\int_a^b u(x)\,v'(x)\,dx = u(b)v(b)-u(a)v(a) - \int_a^b u'(x)\,v(x)\,dx.
Remarks

This is the integral form of the product rule from , typically justified using .