 This video is called Identify Angle Relationships and is a very important video to make sure you understand the different vocabulary words like alternate exterior angles, alternate interior angles, corresponding angles, and consecutive interior angles. These vocabulary words and these relationships for angles are very important that you know them and you understand them in order to have success in Chapter 3. In this picture you can see we have three lines, a vertical line and two horizontal lines. The transversal is always going to be the line that's kind of in a group by itself. This one is alone, it's the only one that's going up and down so we'll call it the transversal. You can see there are eight angles labeled 9 through 16 and within those eight we are going to find these different relationships. Let's start with alternate exterior angles. The word alternate means on the opposite sides and exterior means outside. So alternate we're looking for an angle pair that is on alternate sides of this transversal or opposite sides of the transversal and then exterior says they will be outside of these horizontal lines. So again we're looking for an angle pair opposite sides of that vertical transversal and outside of the horizontal lines. So I see 9 and 16 as a pair and I also see 13 and 12 as a pair. They are outside of the horizontal lines and on alternate sides of the transversal. Now let's talk about alternate interior angles. Well alternate again is on opposite sides of that vertical transversal and interior means they're going to be inside of those horizontal lines. So let's look for some pairs. Angle 10 is inside those horizontal lines. Angle 15 is also inside the horizontal lines and they're on opposite sides of the transversal. So 10 and 15 will be considered a pair of alternate interior angles. What would the other pair be? If you guessed 14 and 11 you're right they're on opposite sides of the transversal inside those horizontal lines. So we have 14 and 11. The next set of angle pairs I'm looking for would be called corresponding angles. Corresponding are where they're in the same position on your graph. So if you take a look at angle 9 it's in the upper left hand corner of what I call of this intersection. Think of it as a street where the transversal means the horizontal it's in the upper left hand corner. What other angle is in the upper left hand corner? But coming from this intersection would be angle 11. So one pair of corresponding angles are 9 and 11. What would a second pair be? Well angle 13 is in the upper right hand corner of my top intersection. Angle 15 is in the upper right hand corner of my bottom intersection. So 13 and 15 would be my second pair. Well what's in the lower left hand corner of each of my intersections? If you guessed 10 and 12 you are right and they would be another set of corresponding and what's the only pair that I've missed? 14 and 16. They are in the bottom right hand corner of my intersections. Our next set of angles we need to look at are called consecutive interior angles. Well interior hopefully you're seeing the pattern we're looking at angles that are inside those horizontal lines. So we're dealing with angles 10, 11, 14, and 15. And consecutive is going to mean that they're next to each other in a sense that they're not alternate. They are not on opposite sides of the transversal but they're going to be on the same side of the transversal. So we're thinking inside those horizontal lines and on the same side of the transversal. So if I'm looking at angle 10 what angle is on the same side of the transversal on it? It would be 11. So 10 and 11 are consecutive interior as well as 14 and 15. Then to finish off this video look at angles 13 and 14. They are up here. 13 is an exterior angle, 14 is an interior one. But notice how they're adjacent. They share a side and then also notice how the side they don't share, the sides they don't share make a straight line. Hopefully you recognize that as being supplementary angles. So we can say 13 and 14 are supplementary. We can also say they are a linear pair. And then to finish up one more angle relationship 12 and 15. Well 12 and 15 they share a vertex they don't share any sides. They look congruent, they're mirror images of each other. So sure enough if you guess that they were vertical, oops excuse me, you were right. This concludes the video identify angle relationships.