Do I understand correctly that you need to prove and you want to prove instead? Then yes, to prove a disjunction, it is sufficient to prove one of the disjuncts.
Having a contrapositive proof in which negation was done by DeMorgan's law, .
Would it be correct to say that in some proofs just one of the cases, ~P or ~Q is true? If so, would it be enough to stop proving when one of the cases was shown to be true?
Thanking you in anticipation