# Lecture 9

GO TO:

## Before the Lecture

• Read Sections 4.2 and 4.3. (Note: Look at the section Outcomes to see what you are expected to get from the reading, perhaps after also some in class help.)
• Watch the videos related to these sections (after reading them):
• Write down all questions about the above topics to bring to our (online) lecture. Comments about the videos are welcome!
• Work on the assigned problems for these sections. (See Related Problems below.) You don't need to finish them, but try to work on as many as you can and the bring your questions to class.

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## Related Problems

All of these are to be turned in on 06/19 (Homework 5) by 11:59.

Section 4.2: Turn in: 5, 8. Discuss in Meeting: 2, 3(a), 6(b).

Section 4.3: Turn in: 14, 16. Discuss in Meeting: 2, 4(a), (b), 9(a), 12, 21.

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## In Class

In class:

• We will discuss the reading and pace.
• I will discuss the main points.
• I will answer any other questions.
• We can work on the HW problems.

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## Outcomes

After the assignment (reading and videos before class) and class, you should:

• understand the there exists a unique'' quantifier, including how to write it without using the $\exists !$ symbol;
• know how to negate a statement of the form $\exists ! x \; (P(x))$'';
• know how to prove there exists a unique'' statement;
• understand ordered pairs and Cartesian products;
• know how to prove statements involving set operations of Cartesian products;
• know how to find truth sets of statements in more than one variable.

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