Angle Trisection -- from Wolfram MathWorld

Angle trisection is the division of an arbitrary angle into three equal angles. It was one of the three geometric problems of antiquity for which solutions using only compass and straightedge were sought. The problem was algebraically proved impossible by Wantzel (1836). Although trisection is not possible for a general angle using a Greek construction, there are some specific angles, such as pi/2 and pi radians (90 degrees and 180 degrees, respectively), which can be trisected. Furthermore

Angle Trisection -- from Wolfram MathWorld

Angle Trisection, adjacent Angle, angle Aigu, angolo Piatto, angle Obtus, compassandstraightedge Construction, isosceles Triangle, internal Angle, right Angle, Compass

Angle Trisection -- from Wolfram MathWorld

Angle trisection - Wikipedia

Trisection of angles-similarly

Angle Trisection Different Modes, PDF, Circle

Wolfram Mathworld in the Notebook Archive

Pascal's Angle Trisection - Wolfram Demonstrations Project

Pat'sBlog: Trisecting the General Angle, A Plethora of Pretty Approaches

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Hippias Logic, Astronomy, Science, and Ideas Too

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Wolfram Mathworld in the Notebook Archive