Uploaded March 2022 | Updated September 2026, 2 weeks ago

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This lecture is part of my Berkeley math 115 course "Introduction to number theory"
For the other lectures in the course see youtube.com/playlist?list=PL8yHsr3EFj53L8sMbzIhhXSAOpuZ1Fov8

We define Gauss sums and use them to give another proof of the law of quadratic reciprocity.

The textbook is "An introduction to the theory of numbers" by Niven, Zuckerman, and Montgomery (5th edition).