# Quick (dumb) Notation Question

I know writing $$\frac{\partial^{1}u}{\partial x^{1}}$$ is "bad" notation, but can I still write the sum:

$$\sum^{n}_{k=1}\frac{\partial^{k}u}{\partial x^{k}}$$

??

THANK YOU

PS. Being able to write LaTeX equations is actually awesome.

CompuChip
Homework Helper
When you write it explicitly it looks a bit weird, but I see no objection to using it in such a sum.

OK. I just wanted to make sure. Thanks!

Can I ask what kind of situation you're getting that sum in?

arildno
Homework Helper
Gold Member
Dearly Missed

When dealing with just the first derivative of some function, it is superfluous, but completely analogical to the case that $x=x^{1}$
Neither of these two notations are "bad" in any way.

HallsofIvy
$$\sum_{k=0}^n \frac{\partial^k u}{\partial x^k}$$
$$\frac{\partial^0 u}{\partial x^0}= u(x)$$