Triangles: CBSE maths class 9.br definition and its figures.br parts of triangle -br vertices, sides and angles.br types of triangles on basis of sides-br equilateral triangle, isosceles triangle, br scalene triangle.br types of triangles on basis of angles-br right-angled triangle, acute-angled triangle,br obtuse-angled triangle.br special type- isosceles right-angled triangle.