Name ________________________   Logic Homework 4  Date ______________

4. For each of these arguments, prove it valid or invalid by truth table.

1.			 	Cf	Dg	‖	Cf	Dg	Cf ^ Dg		
Cf				T	T	‖
Dg				T	F	‖
Cf ^ Dg 			F	T	‖
				F	F	‖

2.				Fh	Gb	‖	Fh ^ Gb		Gb	
Fh ^ Gb			T	T	‖
Gb				T	F	‖
				F	T	‖
				F	F	‖

5.			Hc	Jd	‖	Hc v Jd	~Hc		Jd	
Hc v Jd				‖
~Hc     					‖
Jd					‖
					‖

4					‖						
Kg   		  			‖
Kg v Lf				‖
					‖

If you have trouble, I suggest trying the picture method first. For example, can you place "g" and "f" on the following diagram in a way that makes Kg true and Kg v Lf false?

			K				L

Question 5. Write out the correct definition of validity in your own words as precisely as you can. Try to use different words from the ones you used last time.

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