00:02
Okay, now suppose we have some sets a, b, c, and given a is a subset of b, and b is a subset of c.
00:15
A, b, c, sets, given a is a subset of b, and b is a subset of c.
00:24
We want to show a is a subset of c.
00:29
Now, for any element a which is containing a, as a is a subset of b, you know a must an element in b.
00:44
This is the conclusion from first condition.
00:49
The second one, as b is a subset of c, we know for any element b in b, b must an element in c.
00:57
As from here we know a is an element in b, and i mean this is true for any element in b.
01:06
So from here we know a must be an element in c.
01:12
So what do we know? for any a in a, we must have a is contained in c.
01:19
That is equivalent to c.
01:23
C is a subset of, a is a subset of c.
01:27
So the first data then is very easy.
01:30
Now let's consider the second one.
01:32
Suppose a as a set, we say it is an element in b, and b is an element in c...