Thread: partial derivative question

Say I'm given a function


the function u itself is not defined.

when i take a partial derivative with respect to x, do i just write it as


or is there a chain rule that i have to follow?

Originally Posted by dlbsd

Say I'm given a function


the function u itself is not defined.

when i take a partial derivative with respect to x, do i just write it as


or is there a chain rule that i have to follow?

indeed there is a chain rule.

let and , then you want .

by the chain rule,