I'm trying to use the alignat environment to arrange five equations on three lines as follows: two equations on the first line, two equations on the second line (aligned with those of the first line), and the fifth equation centered on the third line by itself. For what is worth, here's my failed attempt:
\begin{alignat}{3}
a ={}& b
&\qquad &
c ={}& d
\\
e ={}&f
&\qquad &
g ={}& h
\\
{\centering
i = j
}
\end{alignat}
Please note I don't want the equation i=j
on the third row to be aligned to the left, nor to the right, nor aligned with any particular piece of the other four equations, I really want it by itself on the third row, and centered on that row. I can produce the first two lines with no problem (using either align or alignat), but I can't get the single equation on the third line to be centered!