Triangle Ajnala(b) Amritsar

Triangle Geometric figure consisting of three points, called vertices, connected by three sides. In Euclidean plane geometry, the sides are straight line segments. In spherical geometry, the sides are arcs of great circles . See Geometry; Trigonometry. The term triangle is sometimes used to describe a geometric figure having three vertices and sides that are arbitrary curves

Types of triangle 

Triangles are classified in terms of their sides and angles. Scalene triangles have no equal sides (fig. 1), isosceles triangles have two equal sides (fig. 4), and equilateral triangles have three equal sides (fig. 5). In acute triangles, all the angles are less than 90° (fig. 1). In right triangles, one angle is equal to 90° (fig. 3). In obtuse triangles, one angle is more than 90° (fig. 2). A line is called an altitude if it is drawn from a vertex perpendicular to the opposite side (fig. 6). A line is called a median if it is drawn from a vertex to the midpoint of the opposite side (fig. 7). A line is called an angle bisector if it divides an angle into two equal angles (fig. 8). A line is called a perpendicular bisector if it is drawn perpendicular to a side through its midpoint (fig. 9). A triangle drawn on the surface of a sphere is called a spherical triangle (fig. 10). A figure with three arbitrary curves is sometimes called a triangle (fig. 11).