[Tex/LaTex] displaymath/split environment with three columns

Question

I am writing the following equation:

\begin{displaymath}
\begin{split}
  MA &= MAAMB + MACAMB\\
  \Leftrightarrow MA &= (MAAM + MACAM)B\\
  \Leftrightarrow (MAAM + MACAM)^{-1}MA &= B
\end{split}
\end{displaymath}

The problem is that I cannot introduce another & to separate the equivalent sign (the \Leftrightarrow) from the line itself; i.e. to create a distance between the sign and the beginning of the formular. I want that the equivalent signs are aligned similar the the equal signs. Is there a way to accomplish this?

I read somewhere that the eqnarray is deprecated? Is this true? Even using an eqnarray is not optimal, because the cells are left aligned.

Answer 1

What you are looking for is the alignat* environment:

\begin{alignat*}{2}
&                       &MA                    &= MAAMB + MACAMB\\
&  \Leftrightarrow\quad &MA                    &= (MAAM + MACAM)B\\
&  \Leftrightarrow      &(MAAM + MACAM)^{-1}MA &= B
\end{alignat*}