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Revisited: arctan1 + arctan2 + arctan3 \(= \pi\)

by Michael W. Ecker (Pennsylvania State University, Wilkes-Barre Campus)

This article originally appeared in:
College Mathematics Journal
May, 2006

Subject classification(s): Geometry and Topology | Plane Geometry | Triangles
Applicable Course(s): 2.2 Trigonometry

A three-fold construction is given for constructing the angles on the left side of the identity. The geometry of the construction is then used to prove the identity.

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