Theory of Numbers: Congruences and Primitive Roots

This lecture is part of an online undergraduate course on the theory of numbers. We define primitive roots, and show that all primes have primitive roots. Correction: At 16:00 two of the square roots of 1 should be (2^k)/2 +1, (2^k)/2-1, not 2^k/2, -2^k/2. For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EFj52Qf7lc3HHvHRdIysxEcj1H