Visual Derivation of a Trigonometric Identity

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


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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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