[Tex/LaTex] Automatic split and left align a long equation

alignequations

I have a long equation. I want to split and align left for that equation such that same "=" location. I used below code in latex. But it fails to display. Thanks

\documentclass[preprint,12pt, sort&compress]{elsarticle}

\usepackage{mathtools}
\DeclarePairedDelimiter{\norm}{\lVert}{\rVert}
\DeclareMathOperator{\tr}{tr}

\usepackage{lipsum} % for dummy text

\begin{document}

\lipsum[1]
 \begin{equation*}\label{proof_lemma:3} 
            \begin{aligned}
            \frac{\partial E(\mu,\sigma,\theta,\beta)}{\partial \beta}=\int_\Omega \sum_{i=1}^N \frac{\partial r_i(x)}{\partial \beta}dx \\
            =-\int_\Omega \sum_{i=1}^N \left( \frac{( \mu-\sigma- \theta)}{\sigma_i}\right)dx\\
    -\int_\Omega \sum_{i=1}^N \left( \frac{( \mu-\sigma- \theta)}{\sigma_i}\right)dx-\int_\Omega \sum_{i=1}^N \left( \frac{( \mu-\sigma- \theta)}{\sigma_i}\right)dx-\int_\Omega \sum_{i=1}^N \left( \frac{( \mu-\sigma- \theta)}{\sigma_i}\right)dx
            \end{aligned}
             \end{equation*}
\end{document}

enter image description here

Best Answer

Use the ={}& trick:

\documentclass{article}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage[mathscr]{euscript}
\usepackage{mathtools}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{chngcntr}
\usepackage{apptools}
\usepackage{amsthm}
\usepackage{hyperref}

\newcommand{\diff}{\mathop{}\!d}

\begin{document}

\begin{equation*}
\begin{aligned}
\frac{\partial E(\mu,\sigma,\theta,\beta)}{\partial \beta}
={}& \int\limits_\Omega \sum_{i=1}^N \frac{\partial r_i(x)}{\partial \beta}\diff x \\
={}& -\int\limits_\Omega \sum_{i=1}^N \left( \frac{( \mu-\sigma- \theta)}{\sigma_i}\right)\diff x
     -\int\limits_\Omega \sum_{i=1}^N \left( \frac{( \mu-\sigma- \theta)}{\sigma_i}\right)\diff x\\
   & -\int\limits_\Omega \sum_{i=1}^N \left( \frac{( \mu-\sigma- \theta)}{\sigma_i}\right)\diff x
     -\int\limits_\Omega \sum_{i=1}^N \left( \frac{( \mu-\sigma- \theta)}{\sigma_i}\right)\diff x
\end{aligned}
\end{equation*}

\end{document}

Note how I defined a macro for the differential symbol and used \int\limits in order to push the Omega below the integral symbol, which is customary in this case.

Note that hyperref should be loaded last among the packages you have.

enter image description here