Solving Del Cross Question: Why is del x dB/dt = mu dJ/dt?

[miew]

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 :(

Homework Equations

The Attempt at a Solution

 

[tiny-tim]

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

 

[miew]

Thanks ! that makes sense :)