Write $\neg(\phi\land\psi)$ in disjunctive normal form.

Question

Let $\phi,\psi$ be atomic formulas. How do I write $\neg(\phi\land\psi)$ in disjunctive normal form? I can simplify the formula in order to get $\neg\phi \lor\neg\psi$, but what do I do then? This is my first exercise on this matter and some supposedly harder ones were actually easier to solve than this one, probably because I'm forgetting some rule and some obvious points.

Can I just write $(\neg \phi \land \neg \phi)\lor(\neg \psi \land \neg\psi)$?

Answer 1

After the first step, you are done because $\lnot \phi \lor \lnot \psi$ is already in disjunctive normal form.