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: A Math Problem Claimed to Not be Solvable and Has Not Been Solved for Over 2200 Years is Solved by Mahesh Bubna in 2022

Trisecting an Angle Using a Conchoid - Wolfram Demonstrations Project

Angle Trisection -- from Wolfram MathWorld

Angle Trisection Different Modes, PDF, Circle

Angle Trisection -- from Wolfram MathWorld

Angle Trisection Different Modes, PDF, Circle

Triple Point -- from Wolfram MathWorld

Angle trisection - Wikipedia

Wolfram Mathworld in the Notebook Archive

Angle Trisection -- from Wolfram MathWorld

Angle trisection - Wikipedia

Remembering Martin Gardner—Wolfram