Disjunction with Contradiction

Theorem
A disjunction with a contradiction:


 * $p \lor \bot \dashv \vdash p$

Proof

 * align="right" | 4 ||
 * align="right" | 3
 * $p$
 * $\bot \mathcal E$
 * 3
 * align="right" | 5 ||
 * align="right" | 1
 * $p$
 * $\lor \mathcal E$
 * 1, 2-2, 3-4
 * }
 * $\lor \mathcal E$
 * 1, 2-2, 3-4
 * }
 * }


 * align="right" | 2 ||
 * align="right" | 1
 * $p \lor \bot$
 * $\lor \mathcal I_1$
 * 1
 * }
 * }
 * }

Proof by Truth Table
We apply the Method of Truth Tables to the proposition.

As can be seen by inspection, in each case, the truth values in the appropriate columns match for all models.

$\begin{array}{|c|ccc||c|ccc|} \hline \bot & p & p & \lor & \bot \\ \hline F & F & F & F & F \\ F & T & T & T & F \\ \hline \end{array}$