Dear all, I am new to this forum and this is my first post. I hope this is the right place to open this topic. I have a homework for my mathematical methods for physics course and i am kind of stuck into a question: v=ψ∇β show that ∇xv is perpendicular to v. Here v is a vector x is cross product ∇ is gradient vector operator ψ and β are non-vectoral functions I know it seems obvious, but i need mathematical proof which probably contains some identities of triple cross product with del operator. Like i said, i couldn't figure it out. Already now, i want to thank you for all your help.