• Announcements: Hello! As in previous lectures, please watch the videos below in order, and remember to pause as needed if you do not understand something. If you are not able to work it out on your own, send me an email or look for me on Zoom during office hours and I will be happy to discuss the details with you.

• Video 1: Recap of injective, surjective, bijective functions
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• Video 2: Finite, infinite, countable, and uncountable sets
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• Video 3: Alternative definition of infinite set
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• Video 4: Infinite subsets of countable sets are countable
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• Video 5: Countable unions and finite cartesian products of countable sets are countable
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• Video 6: Rational numbers form a countable set and example of an uncountable set
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• Lecture Notes (static file from above videos): PDF file