In an equation, I want to display three points like "…", but instead of horizontally, they should be diagonally. I'm sure there must be a command to do that, but a google search did not really help.
Any idea?
[Tex/LaTex] How to type three points diagonally
math-modesymbols
Related Solutions
One option using \overset:
\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\begin{document}
\[
\partial_0\quad \overset{\leftrightarrow}{\partial_0}
\]
\end{document}
The \sqrt command takes as a mandatory argument what's to be extracted the square root of.
So the correct syntax is
\sqrt{a+b}
not \sqrt(a+b). Your problem is solved by using
Q^*=\sqrt{\frac{2K\lambda}{h}}
If you need the cube root (or other roots), there's the optional argument:
\sqrt[3]{a}
In a previous version of your question you had \sqrtsign: this macro actually exists for historical reasons, but is not documented and should not be used in documents.
Best Answer
The command is called
\ddots. See also How to look up a symbol or identify a math symbol or character? (esp. detexify).