1) Which of the following expressions are wffs (well-formed formulas)?

a)

b) ((A (B'))

c) )

d)

2) Use a truth table to show that is a tautology.

A B            
T T            
T F            
F T            
F F            

3) If P and are true, then what can you infer?

4) If Q' and are true, then what can you infer?

5) Justify each step in the proof sequence of

1. A'

2. B

3.

4.

5.

6.

7. C

6) Using propositional logic, prove the validity of the argument

7) Deduction method: For a valid argument of the form

,

we can prove

instead.

Why?