## Assignments for Weeks 8 and 9

### Reading

Read Chapter 4.
Deemphasize the non-obtuse-angle theorem (pp. 185-186) and "Note for
advanced students" (from p. 188 through the top of p. 190).
Also, we will not have time to study the proofs in this chapter as thoroughly
as those in Chapter 3; however, the **statements** of the propositions
(especially in the Saccheri-Lambert sections at the end) are very important
for understanding later chapters.

### Discussion questions

Each team is responsible for leading the class discussion of one of the
propositions in the main text left as exercises:
- ETA -- Prop. 4.5 = Ex. 8
- THETA -- Prop. 4.6 = Ex. 9
- IOTA -- Prop. 4.7 = Ex. 10
- KAPPA -- Prop. 4.8 = Ex. 11
- LAMBDA -- Prop. 4.9 = Ex. 12
- MU -- Prop. 4.10 = Ex. 13

### Homework due Thursday, March 31 (in Week 10)

- Exercise 4, p. 193.
- Exercise 6, p. 193.
- Exercise 19, p. 197. What would happen if the plane is NOT
semi-Euclidean? (See pp. 185-186. In the theorem there, note that the
"so that ..." applies to the whole statement, not just to the acute angle
hypothesis.)
**(W)**
- Exercise 30, p. 199. (READ Exercise 28 first.)
- Exercise 32, p. 199.