Hello, chopet!
It would help if you copied it correctly!I saw a manipulation that goes like this: . . . . . I bet you didn't!
Not familiar with this one...can anyone enlighten me?
It actually says: .
Let's say we have a multivariable function: .
. . is function of both and
Take the partial derivative with respect to
Now take the partial derivative of that with respect to
This can be written: .