1. The problem statement, all variables and given/known data Given that the divergence of a vector C = 0, show that there exists a vector A such that C = curl A. 2. Relevant equations See above. 3. The attempt at a solution No clue. Can this be proved with introductory vector calculus? That's all I know, including many of the vector-calculus identities. I don't know anything about differential topology, Poincare's Lemma, etc. I assume that somehow A has to be constructed, but that's as far as I get. Thank you.