To create the circle inside the triangle, right click once and drag to create the base of the triangle in any desired direction. Then move up (or down) to create the peak of the triangle. You have now created a nine point circle inside a triangle. The point labeled, O, is the orthocenter of the triangle. To change the size of the nine point circle, highlight and drag a side of the triangle. Notice how the circle changes size and location depending on the size and shape of the triangle. Have fun!