Answer
for answer see step by step
Work Step by Step
If we apply the operation for forming the dual twice to a proposition,
then every symbol returns to what it originally was.
The /\ changes to the V, then changes back to the /\.
Similarly the V changes to the /\, then back to the V.
The same thing happens with the T and the F.
Thus the dual of the dual of a proposition s, namely (s*)*, is equal to the original proposition s.
