Prove that the sum of the squares of the diagonals of parallelogram is equal to the sum of the squares of its sides.

Prove that the sum of the squares of the diagonals of parallelogram is

1.	Prove that the sum of the squares of the diagonals of parallelogram is equal to the sum of the squares of its sides.
Answer» Prove that the sum of the squares of the diagonals of parallelogram is equal to the sum of the squares of its sides.