The maximum area of some triangle(stage a).

The applet allows to investigate the task : Finding the location of the point O inside the triangle(on a parallel basis BC), for which the area of some triangle is maximum. The point O lies on the parallel line, and it can be dragged on this line. When the point O is dragged on the parallel line, the area of the triangle EOD is changed. At each stage of dragging the point O, the area of the triangle and the magnitude of the angles and appear on the screen. The maximum area of is obtained when ED is parallel to the base.