In this article you will find out the Theorem of Class 9 from the Chapter 8 Quadrilaterals. We hope that this will help you to gain extra marks in your examination.
Some Important Points about Quadrilaterals
Definition: A quadrilateral is a polygon with four sides and four vertices.
Types of quadrilaterals: Quadrilaterals can be classified into various types based on their properties, such as parallelograms, rectangles, squares, trapezoids, rhombuses, and kites.
Sum of interior angles: The sum of the interior angles of any quadrilateral is always 360 degrees. This means that the measures of all the angles inside a quadrilateral add up to 360 degrees.
Quadrilaterals Theorems and Proofs Class 9
Theorem 8.1 : A diagonal of a parallelogram divides it into two congruent triangles.
Theorem 8.2 : In a parallelogram, opposite sides are equal.
So, AB=DC and AD=BC (CPCT)
Theorem 8.3 : In a parallelogram, opposite sides are equal.
Theorem 8.9 : The line segment joining the mid-points of two sides of a triangle is parallel to the third side.
Theorem 8.10 : The line drawn through the mid-point of one side of a triangle, parallel to another side bisects the third side.
