# 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.

## Construction

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

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