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Line 1: − [[Image:Triangle.Equilateral.svg|right]]An '''equilateral [[triangle]]''' has, by definition, three sides that are equal in length. − In classical [[geometry]] it can easily be proved that an equilateral triangle is also ''equiangular,'' that is each of its three angles is equal; since another theorem states that the three angles of a triangle total 180°, each angle is 60°. − − In some geometries (like [[sphere]] surface geometry) an equilateral triangle can have angles being more than 60° each: for example the North pole, the point situated 0°N 0°E and the point situated 0°N 90°E form an equilateral triangle with angles of 90°. This can be seen pointing for example the North Pole, Sao Tome & Principe and Singapore on a [[globe]]. − − Note that it is only ''triangles'' that have the characteristic that equilateral means equiangular. For [[polygon]]s of more than three sides, this is not true. A quadrilateral can have four equal sides—be a [[rhombus]]—without necessarily being a [[square]]. − − − [[category:Plane Geometry]]
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