A perpendicular line segment All that passes through the mid point of another linea called the perpendicular bisector of PQ Classification of Triangles You know now that a portion covered by three line segments is called a triangle Look at adjoining figures of triangles in the first fig a three sides are equal in the second Some Special Quadrilaterals b two of the sides are equal But in the third fig c all three sides are unequal Here are some special quadrilaterals Square A equal sides b 4 right angles 4 WI GA 4 In the same way in fig d triangle has all three acute angles fig e contains a right angle and triangle has an obtuse angle Hence all triangles can be named on the basis of measurement of sides or angles Types of Triangles at the Basis of Sides 0 A triangle that has all three its sides unequal is called a scalerie triangle Fig c A triangle that has two of its sides equal is called isosceles triangle Fig b i A triangle that has all three sides are equal is called equilateral triangle Fig a Types of Triangles at the Basis of Angles 1 If each of a triangle is less than 90 then the triangle is called an acute angled triang Fig d i If any one angle in a triangle is right angle ie of 90 then the triangle is called a angled triangle Fig e i If any one angle in a triangle is an obtuse is larger than then the triangle is an obtuse angled triangle fig f Quadrilaterals A polygon made of four straight edges and four corners vertices is called a quadrilateral Given polygon ABCD is a quadrilateral as it has four 0 Sides AB BC CD DA i Angles ZA ZB ZC ZD i Vertices A B C D When you look around yourself you find many quadrilateral figures in your daily life Examples Your study table on which you study and acquire knowledge the picture frame which your picture looks attractive bedsheet which you use to have a sound sleep or a kite alla in the quadrilateral shape 52 Properties of a Square a Diagonals of square are equal b Diagonals of square are perpendicular to each other c Diagonals bisect each other i Rectangle X a 2 pairs of opposite equal sides b 4 night angles Properties of Rectangle a Opposite sides of a rectangle are equal and parallel b Diagonals of a rectangle are equal e Diagonals of a rectangle bisect each other ii Khombus a 4 equal sides b Opposite sides are parallel c Opposite angles are equal Properties of Rhombus A Opposite angles of a rhombus are equal 6 The diagonals of a shombus are perpendicular bisector of each other iv Parallelogram a 2 pairs of opposite equal sides b Opposite siden are parallel c Opposite angles are equal Properties of a Parallelogram a Opposite sides of a parallelogram are equal b Opposite angles of a parallelogram are equal c Diagonals of a parallelogram bisect each other Do You Know Square is a special kindvof parallelogram