Hint for Section 1.2 Question 6

6. There are two statement variables so the truth table will have 4 rows. Start by filling in all possible combinations of truth values for p and q.

p q   p implies.jpg (563 bytes) q q implies.jpg (563 bytes) p   (p implies.jpg (563 bytes) q) L (q implies.jpg (563 bytes) p) p iff.jpg (642 bytes) q
T T            
T F            
F T            
F F            

Now use the truth values in columns 1 and 2, and the definition of  implies.jpg (563 bytes)   to fill in columns 3 and 4.

p q   p implies.jpg (563 bytes) q q implies.jpg (563 bytes) p   (p implies.jpg (563 bytes) q) L (q implies.jpg (563 bytes) p) p iff.jpg (642 bytes) q
T T   T T      
T F   F T      
F T   T F      
F F   T T      

Now use columns 3 and 4, and the definition of L to fill in column 5. Then use columns 1 and 2, and the definition of  iff.jpg (642 bytes) to fill in the final column. Then compare the truth values in columns 5 and 6.

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