# I Kronecker Delta and Gradient Operator

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1. Jan 8, 2017

### maxhersch

I am looking at an explanation of the gradient operator acting on a scalar function $\phi$. This is what is written:

In the steps 1.112 and 1.113 it is written that $\frac {\partial x'_k} {\partial x'_i}$ is equivalent to the Kronecker delta. It makes sense to me that if i=k, then the expression is equal to 1 but why would it be 0 if they are not equal? Perhaps I'm not looking at it the right way but any explanation would be appreciated.

Thanks.

2. Jan 8, 2017

### ShayanJ

Just think about Cartesian coordinates. What is $\frac{\partial x}{\partial y}$ equal to?