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 vice-versa.
6. Diagonals of a rectangle bisect each other and are equal, and vice-versa.
7. Diagonals of a square bisect each other at right angles and are equal, and vice-versa.
8. Mid-point Theorem : The line segment joining the mid-points of any two sides of a triangle is parallel to the third side and is half of it.
9. A line through the mid-point of a side of a triangle parallel to another side bisects the third side.
10. The quadrilateral formed by joining the mid-points of hte sides of a quadrilateral, in order, is a parallelogram
IX Quadrilaterals CCE Test papers