I would have to say my favorite theorem is the Squeeze Theorem. It states that if g(x) <= f(x) <= h(x) and the limit of both g(x) and h(x) as x approaches a is some number, L, then the limit of f(x) as x approaches a is also L.
It seems like an obvious and basic theorem, but it can come in handy more times than you think.
--Jrendall 11:36, 19 January 2009 (UTC)
