- by contradiction
- by ( mathematical ) induction.
The first lecture starts with 20 min or so admin trivia which is only relevant for students who are actually doing the course at UCCS. The mathematics in this lecture starts with the WOP and ends with a proof by induction of the sum of an arithmetic sequence. See also: five proofs of the sum of 1,2,3, ..., n.
The required textbook for Math 311(0) is Elementary Number Theory by David Burton ( 7th ed. ).
Mathematics, an intellectual instrument. ( David Borton, History of Mathematics )