@article {MATHEDUC.06060226,
author = {Forster, Colin},
title = {Trigonometry without right angles.},
year = {2012},
journal = {Mathematical Spectrum},
volume = {44},
number = {3},
issn = {0025-5653},
pages = {98-101},
publisher = {Applied Probability Trust (APT) c/o University of Sheffield, School of Mathematics and Statistics (SoMaS), Sheffield},
abstract = {Summary: This article describes how trigonometric functions can be defined for non-right-angled triangles. In particular, the ratios esin, ecos, and etan, corresponding to the sine, cosine, and tangent ratios, are defined for triangles containing a $\pi/3$ angle. Some of the implications are discussed, including the graphs of these functions and the small-angle approximations.},
msc2010 = {G60xx},
identifier = {2012d.00383},
}