\input manmac
\ddanger The remaining problem is to construct a preamble to
support those lines. To the left of the =~signs we want the column to
be filled at the left; to the right of the =~signs we want it to be filled
at the right. There's a slight complication because we are breaking a math
formula into two separate pieces, yet we want the result to have the same
spacing as if it were one formula. Since we're putting the `|&|' just before
a relation, the solution is to insert `|{}|' ↑↑{lbrace rbrace}
at the beginning of the right-hand formula; \TeX\ will put the proper
space before the equals sign in `|${}=...$|', but it puts no space before
the equals sign in `|$=...$|'.  Therefore the desired \<preamble> is

\bye