Hand-in @ lecture #4

1.1.15

\((\lnot q \land (p \to p)) \to \lnot q\) is a tautology iff its negation has any solution:

The proposition negated need both true and false \(q\), so the proposition is a tautology.

1.1.14

\((\lnot p \land (p \to q)) \to \lnot q\) is a tautology, iff its negation has any solution:

Since the proposition negated leads to a solution, the proposition is not a tautology.