# Del Cross question.

## Homework Statement

I have to do an E&M problem, I think I got it, but I made a few steps that I don't really understand. The first one is:

If delxB= muJ
Does
del x dB/dt = mu dJ/dt ??
If so, why ?

I tried using latex, but it didn't work...sorry :(

## The Attempt at a Solution

tiny-tim
Homework Helper
hi miew!

(have a del: ∇ and a curly d: ∂ and a mu: µ )

yes, because derivatives wrt independent variables always commute (ie you can always change the order) …

2/∂x∂t = ∂2/∂t∂x

Thanks ! that makes sense :)