We will review several of these questions at classtime on October 23, so please bring a copy of your work to class.
Please do your own work --- no file sharing is allowed. Whatever you submit must be stored in your brain as well as in your computer files.
Please prove these sequents:
1.
p ^ q |- (p v s) ^ (r v q)
(Use the ^i, ^e, and vi rules.)
2.
(p ^ q) v r |- (p v r) ^ (q v r)
(The proof is a cases analysis, finishing with ve.
Use vi, ^i, and ^e within the two cases.)
3.
p -> r, q -> s |- (p ^ q) -> (r ^ s)
(Use ^i, ^e, ->e.)
4.
p -> r, q -> s |- (p v q) -> (r v s)
(This proof requires nested subproofs. One finishes with ->i;
the other finishes with ve.)