circle inversion

== English == === Noun === circle inversion (plural circle inversions) (geometry, inversive geometry, for a given circle with centre O and radius r) A transformation that maps any point P ≠ O to the point P’ on the ray from O through P for which OP × OP’ = r2, and which maps O to the point at infinity. ==== Synonyms ==== (transformation): inversion ==== Related terms ==== sphere inversion