Element Of(∈) symbol in LaTeX

This symbol is commonly used in mathematics. This symbol looks a bit like the English capital E. This symbol is known by several other names belongs to, member of, etc. You need to use the \in command to print Element Of symbol in a LaTeX document. You don’t need to use any package for this.

\documentclass{article}
\usepackage{amssymb}
\begin{document}
    %use amssymb package for \mathbb{R}
    $$ A_x \in S_n $$
    $$ A_n \in \mathbb{R}   $$
\end{document}

Output :

Element of with two strokes (⋹) in LaTeX

This symbol has no specific LaTeX commands so you will need to create custom commands. For this, you will need the graphicx package. The \ooalign command allows you to create custom symbols. take a look

\documentclass{article}
\usepackage{graphicx}
\newcommand\inn{
  \mathrel{\ooalign{$\subset$\cr\hfil\scalebox{0.8}[1]{$=$}\hfil\cr}}
}
\begin{document}
  $$ \verb|\in|\rightarrow \in \quad \verb|\inn|\rightarrow \inn $$
  $$ A\inn S_n \quad M_{A\inn B} $$
\end{document}

Output :

• Epsilon(ϵ) symbol in LaTeX
• Small Epsilon(ε) symbol in LaTeX