Forumla to find if a point is inside a polygon defined by 4 pairs of latitude/longitude coordinates?

This might be a little more subtle than it appears. For example if the four points were the north pole, the south pole, a point on the equator on the Prime Meridian and a point on the equator on the International Date Line, then which "side" would you consider the in-"side" and which "side" would you consider the out-"side". Unlike on a plane, a simple closed polygon does not divide the sphere into a bounded region and an unbounded region, but into two bounded regions. Are you asking whether or not a particular point lies in the smaller of the two regions?