[Blindmath] set notation in LaTeX

[Andrew Stacey]

On Tue, Jan 25, 2011 at 09:12:20PM -0800, Roopakshi Pathania wrote:

> subset: \subset
> The cup turned to the right side.
> super set: \supset
> The cup turned to the left side.
> proper subset: \subseteq
> Notice that here the short for equal is added to indicate a proper subset.

I think that you've gotten those two the wrong way around.  The symbol
generated by \subseteq is a "cup" turned on its side (open side to the right)
with a line underneath.  The line underneath makes the bottom of the cup look
like an equals sign so the interpretation of "A \subseteq X" is "A is a subset
of X which can be equal to X".  The unadorned symbol, generated by \subset, is
actually ambiguous in meaning as it is sometimes interpreted to mean "A is
a subset of X which can be equal to X" and sometimes "A is a proper subset of
X, so cannot be equal to X".  Thus \subseteq, and its counterpart \subsetneq,
are used when one wishes to resolve this ambiguity merely by symbols.  Often
a text will explain that \subset means "any subset" or "proper subset" since
the ambiguity exists.  If no explanation is given then it is safest to assume
that \subset means **any** subset, which includes the whole set.

(For what it is worth, Wikipedia agrees with me on this one:
http://en.wikipedia.org/wiki/Subset )

Whilst I'm on this topic, may I point out http://tex.stackexchange.com for
TeX/LaTeX questions.

Andrew Stacey