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Sibley Theorem 3.3.3 -- Illustration

Author:
Erik Tou
Here we see how to construct a Saccheri quadrilateral from a given triangle ABC, by constructing midpoints for two sides and dropping perpendiculars to the line formed by the midpoints. Ultimately, the angle sum from triangle ABC is equal to the sum of the summit angles of the Saccheri quadrilateral GHCB.

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