Triangle
A Triangle is one of the basic shapes of geometry: a two-dimensional figure with three vertices and three sides, which are straight line segments. Triangles are studied in trigonometry. A triangle is a 2-simplex (see polytope).
A triangle is called
- equilateral if all its sides have the same length (or equivalently: all its angles are equal)
- isosceles if two of its sides have the same length (or equivalently: two of its angles are equal)
- right if one of its angles is a right angle (90 degrees or π/2 radians)
- obtuse if one angle is bigger than a right one
- acute if each angle is smaller than a right one
A triangle is also a musical instrument of percussion, usually made of steel.