# CMPSCI 250: Introduction to Computation

### David Mix Barrington

### Fall, 2007

# Homework #2 Questions and Answers

#### Question 2.1, 20 September 2007

In Problem 2.6.4 (b), are the ⊂ symbols meant to denote "strict
subset", so that the sets can't be equal? You didn't define that symbol.

Those two occurrences of ⊂ are mistakes -- they each should be the
ordinary subset symbol ⊆. That symbol is usually used to mean "strict
subset" as you say, but I haven't used it at all in the book. In fact in
this example if you interpret them as strict subset the given statement is not
always true.

Last modified 20 September 2007