Visual Derivation of a Trigonometric Identity

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This Demonstration gives a visual derivation of a trigonometric relation between the tangents of any three angles whose sum is .

Contributed by: Tomas Garza (October 2019)
Open content licensed under CC BY-NC-SA


There are a considerable number of trigonometric identities involving angles whose sum is [1]. This is not the case for angles whose sum is .

This Demonstration provides a visual derivation of a particular relation among the tangents of three such angles, which is useful in application to certain problems [2].


[1] CTK Wiki Math. "Advanced Identities." (Oct 7, 2019)

[2] R. B. Nelsen, "Heron's Formula via Proofs without Words," The College Mathematics Journal, 32 (4), 2001, p. 291.


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