# Triangles - Concept Points

Class 9 - Mathematics

1. A plane figure bounded by three line segments is called a

**triangle**.2. A triangle can be:

- equilateral (all three sides are equal)

- isosceles (any two sides are equal)

- scalene (all three sides are unequal)

3. A triangle in which one of the angles measures 90° is called a

**right-angled triangle**or simply a right triangle.4. The sum of the angles of a triangle is always

**180°**5. Two figures are congruent, if they are of same shape and same size. Congruent triangles are exactly identical.