 Another thing we can find, given two points, is the midpoint between them. So if I have two points, again I have the coordinates of the two points x1, y1, x2, y2, then the midpoint between them is going to be located at x1 plus x2 over 2, y1 plus y2 over 2. And if you look at this formula, in some sense what we're doing is we're taking the average of the x-coordinates, we're taking the average of the y-coordinates, and that's going to locate the midpoint. So it's helpful to think about the midpoint as being our average point. So, for example, let's say I have the two points 4, negative 3, and 6, 4. So I can find the midpoint, paper is cheap, so let's go ahead and write down our formula. The midpoint is going to be this value here. And if we compare this to what we have in our formula, we have, let's see, x1, that's our first x-coordinate, x2 is our second x-coordinate. So I have x1 is 4, x2, my second coordinate is 6, y1, that's my first y-coordinate, that's negative 3, y2 is my second y-coordinate, that's going to be 4, and I'll substitute those in, and at this point I have an arithmetic expression. I can evaluate, 4 plus 6 is 10, over 2, negative 3 plus 4 is 1, over 2, and I'll do a little bit of simplification there, that's going to be 5, what half is my midpoint.