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.