# Greatest Hits for HW 6

1. For #14 of section 4.2, a lot of people forgot that R \circ R is a binary relation. Also to describe a binary relation one has to write "(x,y)\in R\circ R \equiv some condition on x,y holds" or an equivalent statement in English (i.e. must specify x,y are the variables being related by R \circ R, otherwise it would be unclear what R \circ R is without knowing who the players are)

2. There was in general much confusions about the notation R \circ R.

3. For the function composition problems serveral people wrote that g cannot be composed with f because the codomain of f does not match the domain of g – but that is not an excuse if it is clear that the image of f falls in the domain of g.

4. There was an incorrect proof by circular reasoning for the universal bound question.