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  1. \item \self Consider the propositional formula $\varphi = (\neg p \imp r) \land (r \imp \neg p) \land q$.
  2. \begin{enumerate}
  3. \item Fill out the truth table for $\varphi$ (and its
  4. subformulas).
  5. \begin{tabular}{|c|c|c||c|c|c|c|}
  6. \hline
  7. $p$&$q$&$r$&$\;\neg p\;$&$(\neg p \imp r)$&$(r \imp \neg p)$&$\quad\varphi\quad$\\
  8. \hline
  9. \hline
  10. \textbf{F} &\textbf{F} &\textbf{F} & \T & \F & \T & \F \\
  11. \hline
  12. \textbf{F} &\textbf{F} &\textbf{T} & \T & \T & \T & \F \\
  13. \hline
  14. \textbf{F} &\textbf{T} &\textbf{F} & \T & \F & \T & \F \\
  15. \hline
  16. \textbf{F} &\textbf{T} &\textbf{T} & \T & \T & \T & \T \\
  17. \hline
  18. \textbf{T} &\textbf{F} &\textbf{F} & \F & \T & \T & \F \\
  19. \hline
  20. \textbf{T} &\textbf{F} &\textbf{T} & \F & \T & \F & \F \\
  21. \hline
  22. \textbf{T} &\textbf{T} &\textbf{F} & \F & \T & \T & \T \\
  23. \hline
  24. \textbf{T} &\textbf{T} &\textbf{T} & \F & \T & \F & \F \\
  25. \hline
  26. \end{tabular}
  27. \item Is $\varphi$ satisfiable? \\
  28. \quad Yes.
  29. \item Is $\varphi$ valid? \\
  30. \quad No.
  31. \item Give a formula $\psi$ that semantically entails $\varphi$. \\
  32. \quad For any formula $\varphi$ it holds that $\bot \models \varphi$, we can therefore choose $\psi = \bot$. We could also represent $\varphi$ as DNF: $(\neg p \land q \land r) \lor (p \land q \land \neg r)$. This is an equivalent formula and therefore semantically entails $\varphi$.
  33. \item Give a formula $\psi$ such that $\varphi$ semantically entails $\psi$. \\
  34. \quad For any formula $\varphi$ it holds that $\varphi \models \top$. We could also again choose $\varphi$ in DNF.
  35. \end{enumerate}