Tomahawk Trisection of an Angle

Let . Let be a semicircle with diameter .
Given any angle where is tangent to at , the straight lines and trisect .
In other words, the triangles , and are congruent.


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This Demonstration is based on [1]. The construction violates the Euclidean constraints on the use of only a straight edge and compass; specifically, by drawing the tangent . The result is true nonetheless since the semicircle radius and . Then .
[1] G. E. Martin, Geometric Constructions, New York: Springer, 1998 pp. 20–21.
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