Basic Level
Areas
The application allows arriving to the formula of the area of a parallelogram using the construction of the rectangle [EBCF] which has the same area as the parallelogram [ABCD].
Moving the leftmost triangle [ABE] along the line containing the line segment [AD] so that the vertex A of the triangle coincides with the vertex D of the parallelogram, we get the rectangle [EBCF]. Thus, the rectangle and parallelogram have the same area, so the area of the parallelogram is equal to the product of the measurements of the line segments [AD] and [BE].