Lecture 5

We discussed some issues from the quiz, most notably:

• Moving type information between hypothesis and quantifier.
• Converting between (A and B) --> not C and (A and C) --> not B
• Checking claims involving divisibility: try small integers, be clear on which number comes first in x|y
• Another nested quantifier example

We also did exercises on

• Constructing proofs by contrapositive and contradiction
• Divisibility in integer linear combinations

Announcements

• WCS first general meeting: Wednesday at 7pm in 3405 (or maybe 3403) Siebel. Be there or be square!
• Some folks missed one or two quizzes due to joining the class late and/or making mistakes getting started with the quiz system. We're going to smooth over most of the damage by dropping the lowest two quiz scores (for everyone in the class). when we compute final quiz averages.
• A tiny handful of people had something more serious happen to them at the start of the term, which prevented them from attending the first week. If you think you're one of these people, fill out this web form by Friday, so we can get all the details.