Adjust the triangle shape by dragging the points A, B, C and the diamond. Examine the area in the context of the containing rectangle, and also by considering the two shown side lengths and their included angle.
Select "Show sub-triangles" and use the rotate slider when the point B is on the edge of the rectangle, and both sliders when point B is beyond the rectangle. Select "Show values" to see the Area Rule () in operation.
Note: if the midpoint of side AB is outside the triangle neither of the sub-triangle constructions included work.