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Been stuck at this for a little... I tried proof by contradiction but got literally stuck at the first step... So hypotheses is ~A and to derive is: ~(AvB) v (~A&B).

Would appreciate any help.

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Proof via Natural Deduction

Made using proofs.openlogicproject.org.

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  • I think the name of that assertion you might be looking for is the law of excluded middle! – thorimur Apr 5 at 18:50
  • @thorimur Ah, exactly what I was looking for. Thank you! – hyper-neutrino Apr 5 at 18:59
  • Many thanks for your reply! While your answer derives the correct conclusion, it's not by way of natural deduction. I am trying to solve this using natural deduction rules such as v.elimination RAA, etc. Any clues? Cheers! – Sal Apr 5 at 19:08
  • @Sal Sorry for the delay; I've never seen natural deduction before, had to go look around to learn what it's about. See my edit; hopefully this is what you needed! – hyper-neutrino Apr 5 at 19:40

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