Proofs with ∨

• “∨” means “or”

• “a ∨ b” means you have a proof of a, or you have a proof of b

• In logic if you can prove a

• then you may conclude a ∨ b

• In logic if you can prove b

• then you may conclude a ∨ b

• (These are called ∨I)

• (We will do ∨E shortly)