Quadrilaterals class 9 – A quadrilateral is a closed figure with four straight sides. The sum of all the interior angles of a quadrilateral is 360 degree. The diagonal splits a parallelogram into 2 triangles which are congruent. Opposite sides and angles of a parallelogram are equal. Also, diagonals of a parallelogram always bisecting each other. A quadrilateral is a parallelogram, if either opposite sides or opposite angles are equal or diagonals are bisecting each other or pair of opposite sides are parallel and equal. In a rectangle, diagonals are equal and bisect each other and vice-versa. In a rhombus, Diagonals bisect each other at 90 degree and vice-versa. In a square, diagonals are equal and bisect each other at 90 degree and vice-versa. In a triangle, the line joining midpoints of any two sides is parallel to the 3rd side and is half of it. A parallelogram is formed by joining the mid-points of the sides of a quadrilateral. Examples of parallelogram: square, rectangle and rhombus. In a trapezium, one pair of opposite sides of quadrilateral is parallel. If both pairs of opposite sides of quadrilaterals are parallel then it is called parallelogram. If one angle of a parallelogram is a right angle then it is called a rectangle. If all the sides of a parallelogram are equal then it is called a rhombus. If all the sides of a parallelogram are equal and angle is 90 degree then it is called a square. A square is both rhombus and rectangle. A trapezium is not a parallelogram but a parallelogram is a trapezium. Also, a rhombus or rectangle is not a square.
Quadrilaterals class 9 Examples