Tautologies and contradictions
Mathematical logic · Mathematics
Study notes
Q: Show p ∨ ¬p is a tautology and p ∧ ¬p a contradiction. p=T: p∨¬p = T∨F = T; p∧¬p = T∧F = F. p=F: p∨¬p = F∨T = T; p∧¬p = F∧T = F. First column all T (tautology - law of excluded middle!); second all F (contradiction).