Objective

This experiment is designed to provide an interactive environment in which students can discover and investigate the important properties of parallelograms.

User´s Guide

By dragging any of the vertices of the parallelogram, students can change either the shape or the size or both at the same time:

1. Drag any of the four vertices horizontally to change the angles between two adjacent sides.
2. Drag any of the four vertices vertically to change the altitude.
3. Drag any of the vertices diagonally to scale the parallelogram in both horizontal and vertical directions.
4. In addition, each of the slider bars can be used to scale the parallelogram horizontally or vertically.
5. The display of diagonals, angles, and related numerical information can be turned on and off anytime.

This interactive environment can generate an unlimited number of different parallelograms providing students the opportunity to discover and observe common properties among all parallelograms.

1. As you drag any of the vertices, observe any pair of opposite angles. Are they equal all the time?
2. As you drag any of the vertices, observe the consecutive angles. Are they always equal? What about their sum (supplementary)?
3. Do the diagonals bisect each other?
4. Can we change a parallelogram into a rhombus by changing the lengths of two adjacent sides to make them equal? Can we say that a rhombus is an equilateral parallelogram?
5. Can we change a parallelogram into a rectangle by making one interior angle a right angle, thus changing all four angles? Can we say that a rectangle is an equiangular parallelogram?
6. Can we change a parallelogram into a square?