Constructing a Parallelogram with a Given Base

Construction Algorithm
1 Construct a line AB as a given base of the parallelogram.
2 Construct a point C above the line AB and the line passing through it parallels AB.
3 Construct a line joining between B and C.
4 Construct a line parallel to BC through point A.
5 Generate the intersection points between the two lines to find the fourth vertex D of the parallelogram.
6 Join up the four points A, B, C and D to get the required parallelogram.
7 Switch to drag mode. Pick a free element. Move it around to check your construction.

Construction Theorem

A parallelogram is a quadrilateral, in which each two opposite sides are parallel.

Please enable Java for an interactive construction (with Cinderella).
Please enable Java for an interactive construction (with Cinderella).