[Tex/LaTex] Multi-line equations with explanations on some lines


I would like something like this:

= STH       REASONS Explained.
= STH.

How can I do this?

Best Answer

If you use the amsmath package then this can be done using the align (or align* if you don't want the equations numbered) environment together with the \text command for the text.


A &= B \\
&= C && \text{Because of D} \\
&= D && \text{But beware of E} \\
&&& \text{Some more on that}
&= F

Result (note that the actual result will be centred on the page):

aligned mathematics

To get the alignment as you have it, you would have:

&A \\
&= B \

at the start.

The amsmath package is loaded by default if you use one of the classes from the AMS, such as amsart.