This applet can be used to see the properties of parallelograms.[br][list][br][*]Drag any of the blue points to change the parallelogram.[br][*]Click the "Duplicate" button to create a copy of the parallelogram.[br]If necessary, adjust the position of the second parallelogram to match the colors of the angles of the original parallelogram.[br][*]Drag the orange point to rotate the copy around the center of the parallelogram.[br][/list][br]Use this symmetry to see the properties of the parallelograms.

[list=1][*]Parallelograms[/*][/list][list][*]Construct a general parallelogram.[br][/*][*]Click on the "Duplicate" button and if necessary, adjust the position of the second parallelogram to match the colors of the angles of the original parallelogram.[br][/*][*]Rotate the second parallelogram on 180 degrees around the intersection point of the diagonals. Use this symmetry to notice the three properties:[/*][*] The opposite sides are congruent[/*][*] The opposite angles are congruent[/*][*] The diagonals bisect each other[/*][/list]