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| | Encyclopedia: Sine (Site not responding. Last check: 2007-10-19) |
 | | They may be defined as ratios of two sides of a right triangle containing the angle, or, more generally, as ratios of coordinates of points on the unit circle, or, more generally still, as infinite series, or equally generally, as solutions of certain differential equations. |
 | | In all of these cases referring to triangles, the triangles are taken to exist in the Euclidean plane, so that the angles always sum to 180°. |
 | | For example, with the above identity, if one considers the unit circle in the Argand plane, defined by e |
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