## triangleA three-sided polygon. The sum of the interior angles of a triangle is always 180°, unless the triangle is drawn in a non-Euclidean geometry (see below). Triangles can be classified either by their angles, as acute, obtuse, or right;
or by their sides, as scalene (all different), isosceles
(two the same), or equilateral (all equal). A right (or
right-angled) triangle has one interior angle equal to 90°, and may
be either scale or isoscles (see Pythagoras'
theorem). ## Related category• POLYGONS | |||||

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