I can't find the LaTeX command and symbol and its package of this symbol. Can any one suggest me the command. I tried \mathcal{F} but its not exactly the same.
[Tex/LaTex] Command for this symbol looks like \mathcal{F}
fontssymbols
Related Solutions
Often, an asterisk (*) is used to denote dates of birth. An example is the German Wikipedia entry for Donald E. Knuth.
The corresponding symbol for dates of death is the dagger (†), produced by, e.g., \textdagger.
Well here is one that looks kinda like cheating, it uses amsmath only, though adding calc will make the definition much simpler:
\documentclass{article}
\usepackage{amsmath}
\newlength{\crossl}
\settowidth{\crossl}{$\times$}
\newlength{\ceql}
\settowidth{\ceql}{$\times=$}
\addtolength{\ceql}{-\crossl}
\newcommand{\crosseq}{\mathrel{\makebox[\crossl][l]{$\times\hspace{-\ceql}=$}}}
\begin{document}
$f(x)\crosseq g(x)\crosseq h(x)$
\end{document}
Result:
One can also play around with the position and the symbols used:
\newcommand{\crosseq}{\mathrel{\makebox[7.7778pt][l]{$\neq$\hspace{-6.7778pt}\raisebox{-2.5pt}{$\backslash$}}}}
EDIT: Since this answer is chose I will add some more solution, this time using egreg's suggestion as poking around with boxes will likely create unexpected spacing issue:
\newcommand{\crosseq}{\mathrel{\ooalign{\hidewidth$/$\hidewidth\cr\ooalign{\hidewidth$\backslash$\hidewidth\cr$=$\cr}\cr}}}
or
\newcommand{\crosseq}{\mathrel{\ooalign{\hidewidth$/$\hidewidth\cr\ooalign{\hidewidth\raisebox{-2pt}{$\backslash$}\hidewidth\cr$=$\cr}\cr}}}
Result:
EDIT2: Add [l] option to \makebox in order to adjust alignment.
Best Answer
Use
euscript's\EuScript: