The green (upper) triangle has an area of . the purple (lower) triangle has an area of . place the orange triangle (square symbols) directly next to the green triangle so that the two triangles together make a rectangle. the total area of this rectangle is , which is the area of the green triangle.

Given: ae ≅ ce ; de ≅ be prove: abcd is a parallelogram. we have that ab || dc. by a similar argument used to prove that △aeb ≅ △ced, we can show that △ ≅ △ceb by. so, ∠cad ≅ ∠ by cpctc. therefore, ad || bc by the converse of the theorem. since both pair of opposite sides are parallel, quadrilateral abcd is a parallelogram.