LaTex problem with matrix left alignment on the margin

Question

I want my matrix to align next to the left margin, but it does not work at all. Here is my code:

\begin{equation}
    E=
    \begin{pmatrix}
        1 & 0 & 0\\
        0 & 1 & 0\\
        0 & 0 & 1
    \end{pmatrix}
    \nonumber
\end{equation}

Thank you in advance.

Answer 1

Two ways; either use the \flalign* environment, from amsmath, or insert \[ …… \] in a fleqn environment, from nccmath:

\documentclass{article}

\usepackage{mathtools, nccmath}
\usepackage[showframe]{geometry}

\begin{document}

\begin{fleqn}
\[
    E=
    \begin{pmatrix}
        1 & 0 & 0\\
        0 & 1 & 0\\
        0 & 0 & 1
    \end{pmatrix}
    \nonumber
\]
\end{fleqn}

\begin{flalign*}
    E & =
    \begin{pmatrix}
        1 & 0 & 0\\
        0 & 1 & 0\\
        0 & 0 & 1
    \end{pmatrix} &
\end{flalign*}

\end{document}