\documentclass{article}
\usepackage{amsmath}
\usepackage{xepersian}
\settextfont{Yas}
\begin{document}
\begin{description}
\begin{LTRitems}
\item[(1)]$\forall a \in S:(a,a) \in \Psi, (a,a) \in \theta \Rightarrow (a,a) \in \Psi \cdot\theta$.
\item[(2)]
$\begin{aligned}[t]
(a,b) \in \Psi \cdot \theta &\ \ \Rightarrow\ \ \exists c \in S:(a,c) \in \Psi, (c,b) \in \theta\\
&\ \ \Rightarrow\ \ (b,c) \in \theta, (c,a) \in \Psi\\
&\ \ \Rightarrow\ \ (b,c) \in \theta\cdot \Psi .
\end{aligned}$
\item[(3)]
$\begin{aligned}[t]
&\begin{cases}
(a,b) \in \Psi\cdot \theta &\Rightarrow \exists x \in S:(a,x) \in \Psi ,(x,b) \in \theta \\
(b,c) \in \theta\cdot \Psi &\Rightarrow \exists y \in S:(b,y) \in \theta ,(y,c) \in \Psi
\end{cases}\\
&\begin{cases}
(x,b) \in \theta \\
(b,y) \in \theta
\end{cases} \Rightarrow (x,y) \in \theta
\qquad
\begin{cases}
(x,y) \in \theta \\
(y,c) \in \Psi
\end{cases} \Rightarrow (x,c) \in \theta\cdot \Psi\\
& (x,c) \in \Psi\cdot \theta \Rightarrow \exists z \in S:(x,z) \in \Psi
(z,c)\ \in \theta
\\
&\begin{cases}
(a,x) \in \Psi \\
(x,z) \in \Psi
\end{cases} \Rightarrow (a,z) \in \Psi
\qquad
\begin{cases}
(a,z) \in \Psi \\
(z,c) \in \theta
\end{cases} \Rightarrow (a,c) \in \Psi\cdot \theta\\
\end{aligned}$
\item[(4)]
$\begin{aligned}[t]
& (x,c) \in \Psi\cdot \theta \Rightarrow \exists z \in S:(x,z) \in \Psi
(z,c)\ \in \theta
\\
&\begin{cases}
(a,x) \in \Psi \\
(x,z) \in \Psi
\end{cases} \Rightarrow (a,z) \in \Psi
\end{aligned}$
\end{LTRitems}
به طور مشابه
$\theta\cdot \Psi$
\end{description}
\end{document}
