00:01
So for this problem, to begin, we have that first step as indicated, where we assume that not p implies q.
00:11
So that's a premise, which i'll just indicate with a p.
00:15
Then we'll assume not q.
00:23
And again, this is going to be a premise.
00:26
For the third step, what we'll do is assume, not p, for reason of proof by contradiction.
00:38
Then, for the fourth step, we have that from 1 and 3, if not p implies q, and not p is the case, then we infer q.
00:57
Or, pardon me, i'm just going to change the way that i'm describing this here.
01:02
So specifically, step 3 was for contradiction, or for indirect proof...