Start off with this INTERACTIVE FIGURE on drawing ellipses and circles. It's surprisingly helpful. Watch my video lesson and check out this SCREENCAST. When you get the chance, take a look at p. 195 in the textbook for an interesting sidebar on satellites. That puts a lot of this together to answer a question you may have always had about worldwide communications.
Source: Hewitt, P. G. (2015). Conceptual Physics (12th ed.). Boston, MA: Pearson.