- #1

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My textbook says that by taking the curl we get:

## 0=\nabla \rho X \nabla \phi ## **

I don't follow. I understand the LHS is zero, by taking the curl of a divergence.

But I'm unsure as to how we get it into this form, from which it is clear that the gradients of ##\rho## and

##\phi## are parallel, since I get:

##\nabla X \rho \nabla \phi ##, I know that the curl acting on a scalar field doesn't make sense, I would get ##\rho \nabla X \nabla \phi ##, taking the scalar field ##\rho## to the left since it can not be operated on by a curl. I don't see how you would get **

Many thanks in advance