Sept. 20, 2006

Simson Line, Wallace Line, of a triangle

Pointwise construction of the Deltoid Enveloped by the Simson Lines According to Fettis

Point of Contact of an Altitude with the Deltoid

Points of Contact of the Deltoid and the sides of the triangle.

Orthopole

Pointwise construction of the Deltoid Enveloped by the Simson Lines According Neuberg

Linkage

Tangential Ellipses Each Rotating on one of the foci

Pole and Polar

Conics Enveloped by Polar of Points of a Circle

If a variable triangle has a fixed nine-point circle and a fixed circumcircle it envelops a conic.