Triangle - GCSE Maths Definition

A triangle is a polygon with three sides, three angles and three vertices. The angle sum of a triangle is 180°.

Some triangles have specific properties that help us to solve a wide range of problems involving them.

• a scalene triangle has three unequal sides, and so three unequal angles

• an isosceles triangle has two equal sides, and so two equal angles
  an isosceles triangle has one line of symmetry

• an equilateral triangle has three equal sides, three equal angles (each 60°) and three lines of symmetry

• a right-angled triangle has one angle of 90° - it could be either scalene or isosceles, but the right-angled means it has many specific properties that are studied as part of the work in GCSE Mathematics on trigonometry

Understanding triangles is important as many real-world problems involve the relationship between three points in space (which can be considered as the three vertices of a triangle) such as the position of a car using GPS.