Translation

Question

Hello all,

I cannot understand the last step. I can get to !EF!EFa. Could someone help, please.

This is from Question paper 2020.02.19, Ques 8a.

Thanks

Answer 1

The negation of EF phi is AG ¬phi. (In words: “Not all paths have a point at which something holds” is the same as “There is a path where at every points the opposite of something holds)

Thus we get AG ¬¬EF a. The double negation cancels itself out. We are left with AGEF a.

Comments

perfect..thank you.