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\begin{document}
\noindent
وسط‌چین:
\begin{gather}
\sum_i^j 123\frac{afasdf}{asdfasdf} + \sin 47 \int \omega + \\
\sum_i^j 123\frac{afasdf}{asdfasdf} + \sin 47 \int \omega + \Theta \Gamma \sum_i^j \sigma 123 a
\end{gather}
راست‌چین:
\begin{eqnarray}
\sum_i^j 123\frac{afasdf}{asdfasdf} + \sin 47 \int \omega + \\
\sum_i^j 123\frac{afasdf}{asdfasdf} + \sin 47 \int \omega + \Theta \Gamma \sum_i^j \sigma 123 a
\end{eqnarray}
چپ‌چین:
\begin{eqnarray}
&&\sum_i^j 123\frac{afasdf}{asdfasdf} + \sin 47 \int \omega + \\
&&\sum_i^j 123\frac{afasdf}{asdfasdf} + \sin 47 \int \omega + \Theta \Gamma \sum_i^j \sigma 123 a
\end{eqnarray}

\end{document}