Factor Principles/Conjunction on Right/Formulation 1/Proof 2
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Theorem
- $p \implies q \vdash \paren {p \land r} \implies \paren {q \land r}$
Proof
By the tableau method of natural deduction:
Line | Pool | Formula | Rule | Depends upon | Notes | |
---|---|---|---|---|---|---|
1 | 1 | $p \implies q$ | Premise | (None) | ||
2 | 2 | $p \land r$ | Assumption | (None) | ||
3 | 2 | $p$ | Rule of Simplification: $\land \EE_1$ | 2 | ||
4 | 1, 2 | $q$ | Modus Ponendo Ponens: $\implies \mathcal E$ | 1, 3 | ||
5 | 2 | $r$ | Rule of Simplification: $\land \EE_2$ | 2 | ||
6 | 1, 2 | $q \land r$ | Rule of Conjunction: $\land \II$ | 4, 5 | ||
7 | 1 | $\paren {p \land r} \implies \paren {q \land r}$ | Rule of Implication: $\implies \II$ | 2 – 6 | Assumption 2 has been discharged |
$\blacksquare$
Sources
- 2000: Michael R.A. Huth and Mark D. Ryan: Logic in Computer Science: Modelling and reasoning about systems ... (previous) ... (next): $\S 1.2.1$: Rules for natural deduction: Example $1.15$