| Construction Algorithm | ||
| 1 |  |
Construct a line AC as a given diagonal of the parallelogram. |
| 2 |  |
Construct M as a midpoint of the diagonal AC. |
| 3 |  |
Construct a free line through M. |
| 4 |  |
Construct a point B on the free line constructed in step 3. |
| 5 |  |
Define a reflection at the point M, then construct the image of the point B by reflection on M to get a point D, the fourth vertex of the parallelogram. |
| 6 |  |
Join up the four points A, B, C, and D to get the required parallelogram. |
| 7 |  |
Switch to Move Mode. Pick a free element. Move it around to check your construction. |
| Construction Theorems | ||
| A parallelogram is a
quadrilateral, in which diagonals bisect each other. Reflection preserves the distance between points. |
||