Theorem -1.A diagonal of Parallelogram dividesit into teo congruent traingles.

Theorem -2.in a parallelogram ,opposite sides are equal..

Theorem -3.If each paie of opposite sides of quadrilateralis eaqual ,then it is a parallelogram.

Theorem -4.In aparallelogram, opposite angles are equal..

Theorem -5.If in aquadrilateral ,each pair of opposite angles is equal,thenit is parallelogram.

Theorem -6.the diagonal of parallelogram are not equal to each other.

Theorem -7.The diagonals of quadrilateral bisects each other..

Theorem -8.if the diagonals of a quadrilateral bisects each other ,then it is a parallelogram.