I want to have a multiline equation, and to annotate the lines, for the purposes of a key, to explain the various steps being taken. I currently use the tag
command, which works fine for short explanations, but if they get too long, then the flow is broken. If I try to include a line break or similar, I get a bunch of errors thrown.
\begin{align*}
\int\frac{\ln x}{x^{10}}\ dx&=-\frac{\ln x}{9x^{-9}}+\frac{1}{9}\int x^{-10}\ dx
\tag{IBP: $u=\ln x$, $dv=x^{-10}dx$, $du=\frac{dx}{x}$, $v=-\frac{1}{9}x^{-9}$}\\
%This tag is too long, I want to split it.
&=-\frac{\ln x}{9x^{-9}}+\frac{1}{81} x^{-9}+C
\end{align*}
Is there a convienent way to make this?
\tag
is intended for user-specified equation numbers (the text is copied by\ref
for example) not really for explanatory notes. However\parbox{3cm}{IBP:....}
would allow line breaks (\intertext
is the intended command here although the layout is different)