Question

verify that p +(pq)' is a tautology

Answer 1

ons of good answers, but to phrase it in a more mundane way: "If it rains, cars gets what. It rained." Then to say that the "cars got wet," is of course a tautology... If someone said "When it rains, cars get wet, and it rained today!" Nobody would then ask "did the cars get wet?" – Andres Mejia Jan 14 '16 at 5:22

2

You'll never be asked to solve the really hard cases, but the general problem of determining whether a proposition is a tautology is actually really hard. It's co-NP-complete, as its complement is (a slight variation on) boolean satisfiability; a proposition is a tautology if and only if there is