Two Points Moving Together - Explained

The first step to building this animation from the lines and points we’ve made in previous exercises is adding another point. This can be any point that you choose. Here I chose to call the point E and have it at (4, 2).

Once you’ve added a point, you need to connect it to one of the two other points with a line. You can choose either point, but the equation to animate the point is easiest if you choose the point that the other line “starts” at, in this case C. To create the line you can use the same equation as for the previous line, simply swapping the new point for one of the ones for the previous line, in this case I switched E in for D.

The same was as we did last time, the next step is to add an equation similar to that for the line but with t switched for T. Notice that Desmos doesn’t ask you to add a slider for T since there is one already! Because we used T for both moving points they’ll each start and end their paths of travel at the same time. If we wanted them to move independently we would need to use a different variable and add a new slider for it.