Lemoine Line Theorem: Triangle, Circumcircle, Tangent, Vertices, Collinear Points. Level: High School, College. Step-by-step illustration.
HTML5 Animation for iPad and Nexus

Tangents to the circumcircle of
triangle ABC, at points A, B, and C, meet sides BC, AC, and BA at
points D, E, and F respectively. Prove that point D, E, and F
are collinear. Click the Next button
above to start the step-by-step illustration.