Squeeze Theorem
The Squeeze Play Theorem (or the Sandwich Theorem) is a relatively simple theorem that deals with calculus, specifically limits.
Theorem
Suppose 
is between 
and 
for all 
in the neighborhood of 
. If 
and 
approach some common limit L as approaches , then 
.
Proof
If is between and for all in the neighborhood of , then either 
or 
for all in the neighborhood of . The second case is basically the first case, so we just need to prove the first case.
If increases to 
, then goes to either or 
, where 
. If decreases to , then goes to either or 
, where 
. Since can't go to or , then must go to . Therefore, .
