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|                               plaintexmathon                                |
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Abbreviation:  ã|noneã%
 
Parameters:    ã|noneã%
 
    ã|Description:ã%
This markup  can be  used to make  the dollar sign  ($) the  valid math mode
indicator as is used in PLAIN  TEX instead of the TEXT1 math mode indicator,
the at sign (@).
 
    ã|Example:ã%
 
\plaintexmathon
$x+y=100$
 
    ã|Notes:ã%
 
Do not use this markup with \monospace.
    If used, it should  be specified at the top of  your document.  You will
need to use the  TEX \catcode markup to change back  to using the at sign as
the math mode indicator:
 
\catcode'44=12
 
For more on the \catcode markup, refer to The TEXbook.