00:01
So let's prove a theorem.
00:03
Let's prove that if alternate interior angles are congruent, then we have two parallel lines.
00:14
So let's draw a figure for some context here.
00:19
So here are two lines and a transversal.
00:25
We call the transversal l.
00:29
Our two lines can be m and n.
00:33
And then let's, right, we can label the angles here.
00:41
Four, five, six, seven, eight.
00:46
All right.
00:48
So again, we are trying to prove that alternate interior angles, if they are congruent, then we have lines that are parallel.
00:56
So let's start with a given.
00:59
All right, so let's say that angle three is, congruent to angle six and then we want to prove right that m is parallel to n and so again we can we can prove this so when we prove these types of things since we're trying to prove a theorem we obviously can't use the theorem to prove it we have to use something uh that we prior that we've previously learned right and so as we go through we will learn or we'll use those different things and so we always start with the given so angle three is congruent to angle six all right there's our our given and again we're going to use a two column proof so we always have our reasons on the left statements on the right so again we need to make a connection with things that we already know so what i'm going to do is i'm going to look for, you know, like corresponding angles, alternate exterior angles, consecutive interior angles, and so forth...