1. Read FOL, pages 91-103 (Sections
4.1-4.4). Do the following problems:
- Page 95, Problem 4.
Hand in your answers on
a disk (in PC/IBM format). Name your files exactly as it is specified
in the problem.
- Page 104, Problem 21.
An example for a similar proof is given on page 102 of FOL. Make sure
to understand this example before attempting to solve this problem.
2. Read FOL, page 112 (Section
4.7).
3. Give a semantic and a syntactic proof
for each of the following valid steps
of reasoning:
- Modus tollens: From "A implies B" and "not B" infer "not A".
- Strenghening the antecedent: From "B implies C" infer "(A and B)
implies C".
- Weakening the consequent: From "A implies B" infer "A implies (B
or C)".