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][br][*]Parallelograms[br][/list][br][list][br][*]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, and the diagonals bisect each other.[/list][br][list=1][br][*]Rectangles[br][/list][br][list][br][*]Click on the "Hide Duplicate" button and drag the blue points to make a rectangle. [br][*]Click the "Duplicate" button to show a copy of the rectangle and, if necessary, adjust the position of the second rectangle to match the colors of the angles of the original rectangle.[br][*]Rotate the rectangle on 180 degrees around the intersection point of the diagonals. Use this symmetry to notice the three properties of the parallelograms. [br][*]Notice the additional property of the diagonals of the rectangle - they are congruent. [br][/list]