Solution to 5.

 

5. Use a truth table to answer the following questions about the following 4 statements.

a) Are 1-3 consistent with 4?
b) Do any of 1-3 individually imply 4?
c) Do 1-3 jointly imply 4?


1.~a

2.bv(a->~b)

3.cv(b<->a)

4.cv~b

 a  b  c  ~a  ~b  a->~b  b<->a  bv(a->~b)  cv(b<->a)  cv~b
 T  T  T  F  F  F  T  T  T  T
 T  T  F  F  F  F  T  T  T  F
 T  F  T  F  T  T  F  T  T  T
 T  F  F  F  T  T  F  T  F  T
 F  T  T  T  F  T  F  T  T  T
 F  T  F  T  F  T  F  T  F  F
 F  F  T  T  T  T  T  T  T  T
 F  F  F  T  T  T  T  T  T  T

a) Are 1-3 consistent with 4?

Yes. In the fifth row all

b) Do any of 1-3 individually imply 4?

1 does not imply 4, as can be seen by the sixth row in which 1 is T and 4 is F
2 does not imply 4, as can be seen by the second row in which 2 is T and 4 is F.
3 does not imply 4, as can be seen by the second row in which 2 is T and 4 is F.

c) Do 1-3 jointly imply 4?

Yes. There is no row on which all of 1-3 are T and 4 is F.