Rule of Distribution/Conjunction Distributes over Disjunction/Left Distributive/Formulation 1/Forward Implication

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Definition

$p \land \paren {q \lor r} \vdash \paren {p \land q} \lor \paren {p \land r}$


Proof

By the tableau method of natural deduction:

$p \land \paren {q \lor r} \vdash \paren {p \land q} \lor \paren {p \land r} $
Line Pool Formula Rule Depends upon Notes
1 1 $p \land \paren {q \lor r}$ Premise (None)
2 1 $p$ Rule of Simplification: $\land \EE_1$ 1
3 1 $q \lor r$ Rule of Simplification: $\land \EE_2$ 1
4 4 $q$ Assumption (None)
5 1, 4 $p \land q$ Rule of Conjunction: $\land \II$ 2, 4
6 1, 4 $\paren {p \land q} \lor \paren {p \land r}$ Rule of Addition: $\lor \II_1$ 5
7 7 $r$ Assumption (None)
8 1, 7 $p \land r$ Rule of Conjunction: $\land \II$ 2, 7
9 1, 7 $\paren {p \land q} \lor \paren {p \land r}$ Rule of Addition: $\lor \II_2$ 8
10 1 $\paren {p \land q} \lor \paren {p \land r}$ Proof by Cases: $\text{PBC}$ 3, 4 – 6, 7 – 9 Assumptions 4 and 7 have been discharged

$\blacksquare$


Sources