• Announcements: Today's class was conducted in-person, but here you will find a sequence of videos covering the same material, as well as a PDF file with the corresponding notes at the end of the page. Please remember that Homework 1 is due tonight by 11.59pm, and both lectures next week will be conducted remotely asynchronously. For the latest updated schedule, please always consult the online day-by-day schedule.

• Video 1: Inclusion-exclusion principle with 2 sets: Download file or watch below

• Video 2: Inclusion-exclusion principle with any number of sets: Download file or watch below

• Video 3: Matching problem: Download file or watch below

• Video 4: Divisibility by different primes: Download file or watch below