• This is a heavy math lecture. What is the Pythagorean Theorm? If you don't remember, better look it up!
• If two swimmers who always swim at exactly the same rate in the water both swim in a stream with a current exactly the same distance 2x (x each way) as seen from the shore, one across and back and the other up and down the stream, which one will win?

Revised October 8, 1997.