How to creat the symbol `\not\Leftrightarrow`?

Question

I want to type the symbol \not\Leftrightarrow. I tried with

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\begin{document}
\[\begin{cases}
A\cdot B \geqslant 0,\\
A \geqslant 0 \end{cases} \not\Leftrightarrow \begin{cases}
 B \geqslant 0,\\
A \geqslant 0.\
\end{cases}
\]
\end{document}

enter image description here

I think, it is not nice. How can I creat that symbol?

Nowadays, you can also use \nLeftrightarrow instead if all you need is this one symbol. — daemontus, Sep 13 '22 at 18:06

score 2 · Accepted Answer · answered Jan 16 '15 at 04:48

There is a standard method for it.

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\newcommand{\notleftright}{\mathrel{\ooalign{$\Leftrightarrow$\cr\hidewidth$/$\hidewidth}}}
\begin{document}
\[\begin{cases}
A\cdot B \geqslant 0,\\
A \geqslant 0 \end{cases} \notleftright \begin{cases}
 B \geqslant 0,\\
A \geqslant 0.\
\end{cases}
\]
\end{document}

enter image description here

How to creat the symbol `\not\Leftrightarrow`?

1 Answers1