This is the 17th video in a series of 21 by Dr Vincent Knight of Cardiff University. In large equations or derivations which span multiple lines, we can use the \begin{align} and \end{align} commands to correctly display the aligned mathematics. Here we use the ampersand (&) command to ensure the equations always line up as desired. We also see how to use the \nonumber command to remove the equation number from intermediate steps in the equation if required. The example given in the video is also provided here as a template. To get started, click here to open the 'Aligned mathematics' example.