Following the question in Can we have x with tilde on top?
Basically, i want to have vector lenght like this
\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\begin{document}
$\| \tilde{x} \| $
\end{document}
The output is:
But how to have another tilde at the bottom of X?
$\| \undertilde{\widetilde{x}} \|$
,$\| \undertilde\widetilde{x} \|$
. Even$\undertilde{x}$
also not working.