Objective : 

To explore similarities and differences in the properties with respect to diagonals of the following quadrilaterals- a parallelogram, a square, a rectangle and a rhombus.

Definition:

It is a quadrilateral where both pairs of opposite sides are parallel. Quadrilateral ABCD is a parallelogram.

Properties :

• A diagonal of a parallelogram divides it into two congruent triangles (▲ ADC is congruent to ▲ ABC).
• Diagonals of a parallelogram bisect each other.
• Opposite sides are congruent (AB = DC).
• Opposite angles are congruent (∠ADC= ∠ABC).
• Consecutive angles are supplementary (∠DAB + ∠ADC = 180°).
• If one angle is right angle, then all angles are right.