Posted by raetsel on May 1, 2009
Recently on #logic via twitter Pete Lewis asked:-
a || b -> !(!a || !b)) ? #logic makes my brain hurt
I did a quick truth table on paper and said yes but turns out I was wrong as I had looked at the wrong columns. Doh! Here’s the truth table and you can see for yourself
|A||B||A || B||!A||!B||(!A || !B)||!(!A || !B)|
The colums A || B and !(!A || !B) are not equivalent.