Rule of Addition/Sequent Form/Formulation 1/Form 1/Proof by Truth Table

Theorem

 * $p \vdash p \lor q$

Proof
We apply the Method of Truth Tables.

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

As can be seen, when $p$ is true so is $p \lor q$.