CISC 204 Lecture Notes - Lecture 3: Complex Instruction Set Computing, Sequent
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E we know that one of the two is true, but we don"t know if it"s the left, right, or both the conclusion has got to be true. We can now prove that disjunction is commutative: p q q p. We can also prove that disjunction can be introduced into an implication: q r p q p r. In class, we proved that: if p implies q, then the conjunction of p and r implies the conjunc- tion of q and r . (p q) (p r q r) We also proved that: suppose both p, and either q or r, is true. We can conclude that either p and q is true, or that p and r is true p (q r) (p q) (p r) Self-study: there are proof strategies on the next page of these notes. Proof strategy: consider (p q) (p r q r)