# [Tex/LaTex] Aligning two columns in one equation!

alignequations

Consider the following

\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{amssymb}

\begin{document}
\begin{align}
X_{n}=\begin{cases}
X_{n}^{I}= t_{1}\nu_{1}^{n}+r_{1}\nu_{2}^{n}, \quad -N\leq n<-d, \\
X_{n}^{II}= t_{2}\nu_{1}^{n}+r_{2}\nu_{2}^{n}, \quad \ -d<n<-1, \\
\end{cases}
\end{align}

\end{document}


how can I make sure that the = sign in the left column is aligned as well as the inequalities on the right?

One option is to try the array environment instead of the cases one.

\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{amssymb}
\begin{document}

$$a_{n}=\left\{% \begin{array}{@{}r@{{}={}}l@{\quad}r@{{\,n\,}}l@{}} X_{n}^{I} & t_{1}\nu_{1}^{n}+r_{1}\nu_{2}^{n}, & -N \leq& <-d, \\ X_{n}^{II} & t_{2}\nu_{1}^{n}+r_{2}\nu_{2}^{n}, & -d <& <-1, \\ X_{n}^{III}& t_{3}\nu_{1}^{n}+r_{3}\nu_{2}^{n}, & 1 <& <d, \\ X_{n}^{IV} & t_{4}\nu_{1}^{n}+r_{4}\nu_{2}^{n}, & d <& \leq N, \\ \end{array}\right .$$

\end{document}