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Evolute of an ellipse

Evolute is the envelope of the normals to a curve. Equivalently evolute of a curve is the locus of all its centers of curvature.


Curve e is evolvent (=involute) of an circle c. Determine a normal line to evolvent e at moving point A. Swich the trace on and determine the envelope of all normals. Theorem: A curve is the evolute of any of its evolvents.

Evolute of an evolvent