Question

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

Answer 1

Triangles. Prove that the sum of the squares of the diagonals of a parallelogram is equal to the sum of the squares of its sides. ... We know that the sum of the squares of any two sides is equal to twice the square of half of the third side together with twice the square of the median which bisects the third side