# Quadrilateral Lesson for Class 9 NCERT

• A figure formed by joining four points in an order is called a quadrilateral.
• A quadrilateral has four sides, four angles and four vertices.

• In this chapter, we will study more about different types of quadrilaterals, their properties and especially those of parallelograms.

• You may wonder why should we study about quadrilaterals (or parallelograms)
• Look around you and you will find so many objects which are of the shape of a quadrilateral – the floor, walls, ceiling, windows of your classroom, the blackboard, each face of the duster, each page of your book, the top of your study table.

• Although most of the objects we see around are of the shape of special quadrilateral called rectangle, we shall study more about quadrilaterals and especially parallelograms because a rectangle is also a parallelogram and all properties of a parallelogram are true for a rectangle as well.

A quadrilateral in which both pairs of opposite sides are parallel is called a parallelogram.

KITE : A quadrilateral in which two pairs of adjacent sides are equal is known as a kite.

• The sum of the angles of a quadrilateral is 360ยบ.
• This can be verified by drawing a diagonal and dividing the quadrilateral into two triangles
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