Triangle Introduction

A triangle is a geometrical figure formed by three lines, which intersect each other and which are not all concurrent. A triangle ABC has six parts namely three angles and their sides namely AB, BC, CA. Triangles can be classified either on the basis of the sides or on the basis of the angles.

Classification on the basis of sides

• A triangle, no two of whose sides are equal is called a scalene triangle.

• A triangle, two of whose sides are equal is called an isosceles triangle.

• A triangle, all of whose sides are equal is called an equilateral triangle.

Classification on the basis of angles

• A triangle each of whose angles is acute is called an acute angled triangle.

• A triangle one of whose angles is a right angle is called a right triangle.

• A triangle with one of its angles as an obtuse angle is called an obtuse angled triangle.