Discovering Some Properties of Parallelograms
Using Geometer's Sketchpad
by David Wise

Note: I recommend that this page be printed out, so that the instructions are easier to follow.

Definition: A parallelogram is a quadrilateral whose opposite sides are parallel.

Click here to link to the parallelogram sketch needed to carry out the investigation.

C-52 The opposite angles of a parallelogram are___________________________________.

C-53 The consecutive angles of a parallelogram are________________________________.

C-54 The opposite sides of a parallelogram are____________________________________.

C-55 The diagonals of a parallelogram are _____________________________of each other.

If you have any questions while trying to complete this investigation, or suggestions that would be useful, especially for use at the high school level, please send e-mail to

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