If sqrt(5-2x^2) <= f(x) <= sqrt(5-x^2) for -1 <= x <= 1, find limit f(x) as x goes to 0.

What exactly is the first step in doing these types of problems? This theorem is the only one that I have trouble with as I missed the day of class when we were discussing it.

<= is less than or equal to. I guess I will have to find the latex codes for these problems.