Lecture 15: Vector Operator Identities (RHB 8.8) There are a large number of identities for div, grad, and curl. It’s not necessary to know all of these, but you are advised to be able to produce from memory expressions for rr, rr, r r, r˚(r), r(ar), r (a r), r(fg), and 1 2 3 4 below.