00:01
When we're starting off with this argument, we're going to have three main variables to consider.
00:08
So we can say it's d of x if x is a dinosaur.
00:14
We can have another e of x.
00:17
If x is extinct, then we have to consider the special case of a dodo bird, which we can denote with the letter d.
00:27
So first of all, how can we write that if x is a dinosaur, then, and it is extinct.
00:36
So like the same technique we've been doing for all x, because we're considering all dinosaurs, if it's a dinosaur, we're going to create a subset.
00:47
If it's a dinosaur, then it implies that it must be extinct.
00:56
However, note that we're not making any assumptions about anything that's not a dinosaur, because if this first part of the conditional is false, then the entire conditional will be true still.
01:08
Next, we can consider the special case of the dodo bird with an oiler diagram.
01:14
So let's start off with the larger subset, which is going to be animals that are extinct.
01:22
So this represents our extinct.
01:25
And then we know that dinosaurs is going to be a subset of that...