When Is the Squeeze(Sandwich) Theorem Used? I am beginning to learn Calculus 1, and I was taught about the squeeze (sandwich) theorem. It seems to me that all the problems given have $\sin$ involved. Is this true? When is the squeeze theorem applied?  
Also, what are the standard "squeeze functions"? For example, I know that $-1\leq\sin(x)\leq 1$ and this is used in a $\sin$-involved problem. Are there other such functions to apply when using the squeeze theorem? 

The squeeze theorem provides an intuitive rule for making statements about the convergence of a given series when it is bounded above and below ("squeezed") by 2 other series which are known to converge.
That you are seeing a lot of examples that use trig functions is purely coincidental. What is even more likely is that most of the examples you see also involve quotients, since the squeeze theorem is often used to prove the existence of a limit where the denominator of a function is zero. But agin, it is a general rule and is not restricted to any particular class of function.
