6.3 Align

For use with multiple equations with horizontal alignment (usually on the equals sign or equivalent). Each line is split into aligned columns with the odd numbered columns being right justified and the even numbered left justified {rl rl rl...}.

Due to the problems with numbered eqnarray in one format (see above) and because so many people use the align environment it is included here for “basic” use (i.e. equivalent use to eqnarray effectively). Any use beyond this is effectively an array type environment which relies on correct alignment and strict line breaking. In some transformations all such alignment will be lost and additional line breaking will occur if required. If you require such an environment in which this will not happen then use an array or matrix.

\begin{align}\label{alignlab}
\sum_{i=1}^{13} 2^i &= 2^1 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 
+ 2^7 + 2^8 + 2^9 + 2^{10} + 2^{11} + 2^{12} + 2^{13}\\
&\quad \text{some calculator use later:}\nonumber\\
&=2 + 4 + 8 + 16 + 32 + 64 + 128 + 256 + 512 + 1024 
+ 2048 + 4096 + 8192 \nonumber\\
&=16382 \qquad\text{text in formulas does not break} 
\end{align}