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The constraint symmetry_by_circle( element e1, element e2 , circle c) declares that e1 is the reflection, or circle inversion, of e2 about circle c. If c has center O and radius r, the inverse of a point P is a point P' on the line OP such that OP' * OP = r*r.

There is a large variety of elements that can be reflected, but quite probably they will have to be defined as loci. See, for instance,, where a conic is inverted about a circle. In particulars, arcs reflected on a circle can result in segments or in rays.

See also symmetry_by_point and symmetry_by_line.


  1. symmetry_by_circle example: source JSXGraph