> I think that integration by parts can also be derived in a similar way but I would have to make a proper blog post with illustrations to make it clear. It lo

> I think that integration by parts can also be derived in a similar way but I would have to make a proper blog post with illustrations to make it clear. It looks not dissimilar to how one might think of Stokes's theorem: https://en.wikipedia.org/wiki/Generalized_Stokes_theorem#Underlying_principle https://en.wikipedia.org/wiki/Generalized_Stokes_theorem#Und... .