Possible Duplicate:
typesetting modulus operator, as in remainder
When \mod is used in
a \cong b \mod c
the extra space between \mod and what precedes it is appropriate. But what if I want to write about the quotient structure \mathbb R\mod {2\pi}? In that case \mod is more like a binary operator. How should one code this to get something with spacing appropriate to the occasion?
$$....$$is depricated. Use\[...\]instead.\mod{<arg>}, there’s\bmod,\pmod{<arg>}and\pod{<arg>}. Take a look at theamsmathmanual (texdoc amsldoc, page 18 (pdf 22), section 5.2).