| |
| | Planar Curves - Numericana |
 | | The parabola is a curve that's constructible with straightedge and compass. |
 | | In general, the pedal of a curve is the locus of the foot of the perpendicular from the pole to a tangent of the curve. |
 | | Equilateral triangles, squares, regular pentagons and hexagons are all constructible with straightedge and compass, but it turns out that regular heptagons, enneagons, hendecagons, or tridecagons cannot be so obtained. |
| home.att.net /~numericana/answer/curve.htm (3757 words) |
|