CBSE Class 9 Maths Parallelograms: Basic Properties
 If the diagonal of a parallelogram are equal,then show that it is a square. .

Please solve in fast
 what is ASA congruence rule

ABCD is a trapezium in which ab is parallel to cd and ad is equal to bc
 IN TRIANGLE PQR, ANGLE PQR =90 DEGREE PR=10CM S IS MIDPOINT OF PR. FIND LENGTH OF QS.
 This Question is from chapter Quadrilaterals. EXPERTS, PLEASE ANSWER THIS AS SOON AS POSSIBLE If APB and CQD are two parallel lines then find the type of quadrilateral formed by the bisectors of the angles APQ, CPQ, QCP, and PQD.

This question is from CIRCLE chapter and the topic for this related question is CYCLIC QUADRILATERALS
AC and BD are two chords of a circle which bisects each other. Prove that
(i) AC and BD are diameters of the circle
(ii) ABCD is a rectangle
 Prove that the diagonals of a rhombus are perpendicular to each other.
 In the figure PQRS is a parallelogram and X, Y are the points on the diagonal QS, such that SX = QY. Prove that quadrilateral PYRX is a parallelogram.
 ABCD is a parallelogram and E is the mid point of side BC. If DE and AB when produced meet at F, prove that AF = 2AB.