Cissoid

Cissoid, a curve of much interest in higher geometry. It may be drawn in the following manner: - A circle is described on a line A B as diameter; the tangent E B F is drawn touching the circle at B, and points C₁, C₂ ..., on this tangent are joined up to A. Such lines all cut the circle at, say, D₁, D₂ ..., and if on these lines AO₁, AO₂ ...., are marked equal to C₁ D₁, C₂, D₂ . . , the points O₁ O₂, ... will lie on the cissoid.