Postby stapel_eliz » Sat Oct 10, 2009 11:55 am
The answer will depend upon how your book or instructor defines a "triangle". A triangle with zero area can be termed "degenerate" (as in, "qualifies technically, but isn't terribly useful") or as "not a triangle" (if a triangle must have positive area). Your instructor should be able to tell you which definition you're expected to use.