Click/tap to change which point to move. Click to make selection 4 to move your mouse/finger anywhere without altering the triangle.
This method utilizes the bisector angle and moves the center of a circle toward the incenter, which is done with all vertices. The size starts at zero, but changes at a constant rate until it is as big as the inradius. The positions of the circle also change at a constant rate to get to the center. The reason it is a constant rate is because the lines don't bend, they only change their positions at a constant rate. Think of it like two dots moving on sides AB and BC, and they get to the end at the same time.
