 This video is called finding area on a graph. It is a part of section 11.1. You're going to see quite a few problems like this where you are given points and you're trying to find the area of the shape. Well, you're going to definitely need graph paper to do problems like this. If you don't have any grid paper of your own, make sure you get some. You can go on to Moodle. We've got some on the margins of the Moodle page. You can print out. It really will make a difference. Because when you're given coordinate points, you have to graph them. Once you graph them, we're going to decide, do we have a square, a rectangle, a parallelogram, an irregular shape? You have to figure out what kind of shape you have so then you can go ahead and find the area. So whenever you're given a problem with coordinates like these, always start by graphing them on grid paper. If you can use real grid paper so you get an accurate drawing, you're going to have a much easier time finding the right answer. So B is at negative 4, 3. So from the origin, you're going to go 4 to the left and 3 up. E is 1 comma 3. So from the origin, you're going to go 1 to the right and 3 up. A is at 3, negative 1. So 3 to the right and 1 down. And R is at negative 2, negative 1. So 2 to the right and 1 down. So go ahead and connect them. It would be smart to label them. B, E, A and R. And when I look at that, I see it becomes very clear that I am dealing with a parallelogram. So now I know what formula I have to use. Area of a parallelogram was the base times height and I had to make sure that the base and the height, oh sorry, that's messy, that the base and the height were perpendicular. I think I'm going to pick my base as R, A. I like these horizontal lines because when you're horizontal or vertical on a graph, you're allowed to just count to find the length. So from R to A, it's 1, 2, 3, 4, 5. From B to E, it's 1, 2, 3, 4, 5. Now the diagonal lines, I'm not allowed to just count to find their length. I'd have to use the distance formula to find their lengths. But I'm feeling pretty lucky because I remembered that the base and the height have to be perpendicular. So it's not even the vertical, the diagonals aren't even the right ones to pick. The height, I'm going to go from this bottom left-hand corner and go straight up or from the top right-hand corner and go straight down because that gets you from the top to the bottom of your shape where both of these would meet at a 90-degree angle. So let me be clear, you don't have to use both of them. You just had to recognize that you could use one of them. I'm showing you your two options. You could also, if you wanted, drop a vertical line down on the outside or put a vertical line up on the outside on the right, all of those would be considered the height. And when you count any of them, you get 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4. So we have just determined that the base is 5 and the height is 4. So to find our area, the base is 5, the height was 4. We get the area of this quadrilateral bare to be 20 units squared. Don't forget your label.