What to do

1. Consider how to sketch the proof skeletons for the following:
   • theorem
        x < > 0 implies exists y such that x * y = 1
     

   • theorem
        x < = y and y < = x implies x = y

   • theorem
        X meets Y U Z (the union of Y and Z) iff X meets Y or X meets Z

2. For bonus credit, do Bonus Exercise 1.

   Bonus credit work is optional (i.e., not required).