The object in this discussion is to find out where this approximation comes from.?

You may have seen in previous courses the statement "for angles theta near zero, sin theta can be approximated by theta." I first saw this in a physics cl when we were talking about pendulums. This approximation of sin theta by theta was completely mysterious to me when I first saw it. (I hadn't had calculus yet.) The object in this discussion is to find out where this approximation comes from