00:01
So we have a list of premises, and i'll list each one as a letter.
00:05
So a is p implies not q.
00:10
B is p or r.
00:18
C is q, and d is s and t, or p or not r.
00:33
And so we want to prove r.
00:38
And lists each rule of inference.
00:50
So for our first step, we need to somehow use c to our advantage to find some information about p, because that's the main premises that we have, that's going to be quite useful.
01:07
So what we need to do is we need to take a and take the contrapositive of it.
01:13
So this would be not, not q implies not p.
01:18
And so this is taking the contrapositive of a.
01:27
And whenever we have a double negation, we can just rewrite that we can get rid of the two knots.
01:34
So this is q implies knot p...