IX Quadrilaterals NCERT solution Key points
CCE Test papers Solve Theorem and Illustrated examples Points to Remember : 1. The sum of the angles of a quadrilateral is 360°. 2. A diagonal of a parallelogram divides it into two congruent triangles. 3. In a Parallelogram: (i) opposite sides are equal (ii) opposite angles are equal (iii) diagonals bisect each other 4. A quadrilateral is a parallelogram, if (i) opposite sides are equal, or (ii) opposite angles are equal, or (iii) diagonals bisect each other, or (iv) a pair of opposite sides is equal and parallel. 5. Diagonals of a rhombus bisect each other at a right angle and viceversa. 6. Diagonals of a rectangle bisect each other and are equal, and viceversa. 7. Diagonals of a square bisect each other at right angles and are equal, and viceversa. 8. Midpoint Theorem : The line segment joining the midpoints of any two sides of a triangle is parallel to the third side and is half of it. 9. A line through the midpoint of a side of a triangle parallel to another side bisects the third side. 10. The quadrilateral formed by joining the midpoints of hte sides of a quadrilateral, in order, is a parallelogram IX Quadrilaterals CCE Test papers 



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