# problem using option fleqn in amsmath package

I'm using the following code. What should I do if I don't want the fixed indent from the left margin of my page? ‎

\documentclass[‎fleqn,oneside‎]{article}‎
‎\usepackage{amsmath}‎
....
\begin{align}
a_1& =b_1+c_1\\
a_2& =b_2+c_2-d_2+e_2
\end{align}

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Set the length \mathindent to zero:

\setlength{\mathindent}{0pt}

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EDIT: you can regulate that distance by setting \mathindent (to 0pt, for example), with a \setlength\mathindent{<value>}

\documentclass[fleqn]{article}

\usepackage{amsmath}
\setlength\parindent{0pt}

\begin{document}
\hrulefill

\begin{align}
a_1 &= b_1+c_1\\
a_2 &= b_2+c_2-d_2+e_2
\end{align}

\setlength\mathindent{0pt}
\hrulefill

\begin{align}
a_1 &= b_1+c_1\\
a_2 &= b_2+c_2-d_2+e_2
\end{align}

\end{document}

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Using Thorsten's method affects the math indent for the whole page. If that's not what you want I would suggest using the nccmath package for fleqn like this:

\documentclass{article}
\usepackage{nccmath}
\begin{document}
\noindent This is text on the page here.\\
\begin{fleqn}[0pt]
\begin{align*}
a_1 &= b_1+c_1 \\
a_2 &= b_2+c_2-d_2+e_2\\
\end{align*}
\end{fleqn}
This is more text on the page down here.\\
\end{document}

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Be careful using the nccmath package as I have had several problems using it. See this question for a list of them –  Peter Grill Aug 5 '11 at 4:44

Just to make this complete (I found an easy answer only after a lengthy search): the standard length of \mathindent (in KoMa scrbook class) is <\leftmargini minus \leftmargini>. The rubber part is essential for longer equations.

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You have to determine the length \mathindent. See code below for an example.

\documentclass[fleqn]{article}
\usepackage{amsmath}

\setlength{\mathindent}{\parindent}

\begin{document}
\begin{align}
a_1 &= b_1+c_1 \\
a_2 &= b_2+c_2-d_2+e_2
\end{align}
\end{document}

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