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Tangent formula

From Encyclopedia of Mathematics
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A formula establishing the dependence between the lengths of two sides of a plane triangle and the tangents of the halved sum and the halved difference of the opposite angles. The tangent formula has the form

Sometimes the tangent formula is called the Regiomontanus formula, after the scholar who established this formula in the second half of the 15th century.


Comments

References

[a1] M. Berger, "Geometry" , 1–2 , Springer (1987) (Translated from French)
[a2] E.W. Hobson, "Plane trigonometry" , Cambridge Univ. Press (1925) pp. 158
How to Cite This Entry:
Tangent formula. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Tangent_formula&oldid=31425
This article was adapted from an original article by A.B. Ivanov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article