[Tex/LaTex] align* but show one equation number at the end


I am using align*, but I still need an equation number. I know one solution is to use align and add \nonumber to all lines but the last. Is there a 'lazy' way to do it?

I searched a little and found similar ones suggesting use split:
Show equation number only once in align environment

Unfortunately, due to the page break issue I have, I need to use align, because split won't auto page break, as described in Long equation does not page break.

Best Answer

Use \tag:

a &=b \\
  &=c \numberthis \label{eqn}
Equation \eqref{eqn} shows that $a=c$.
d = e

See page 3 of the amsmath package documentation for details.