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Cardioids from many angles |
 | | Cardioid (heart-shaped) is a curve with a characteristic shape which is variably described as "vaguely resembling heart", "kidney bean like", or "apple cross-section." The curve was named by Johann Castillon in a treatise that appeared in 1741. |
| | The cardioid may thus be described as the locus of all points symmetric to a fixed point (A) on a circle with respect to all possible tangents to that circle. |
| | We then conclude that the similarity transformation with the center at A and coefficient 1/2 transforms the cardioid into the locus of feet of the perpendiculars dropped from A onto all the tangents of the stationary circle. |
| www.cut-the-knot.org /ctk/Cardi.shtml (993 words) |
