MATH 3220 § 1	THIRD HOMEWORK ASSIGNMENT	Due Monday,
A. Treibergs		September 10, 2007.

You are responsible for knowing how to solve the following exercises. Please hand in the starred "*" problems.

Exercises from the text "Foundations of Analysis" by Joseph L. Taylor. 7.2 [ 12*, 13*, 16 ] 7.3 [ 1, 2 ] Additional exercises. A*   Let a, b and c be real numbers such that a2 + b2 = 1. Let      £ = { (x,y) ∈ R2: ax + by = c} be the points on a line in the plane. Show that £ is a closed set.   B*   Let S=∪n=1∞{xn} be the set in R2 consisting of points from the sequence xn=( 1/n, 1/n ). Determine whether S is open, closed or neither. Prove your answer.