Prove that in a parallelogram, the sum of the squres of the diagonals is equal otthe four times the sum of the square of three conterminos edges.

Prove that in any parallelogram, the 'sum of the squares of all sides is equal to the sum of the squares of the diagonals'.

In a paralledogram, the sum of the square of the lengths of the diagonals is equal to sum of the squares of the lengths of its sides.

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

Prove that the sum of the squares of the diagonals of a rhombus is equal to the sum of the squares of the sides.

Prove that three times the sum of the squares of the sides of a triangle is equal to four times the sum of the squares of the medians of the triangle.

Prove that in any parallelogram the sum of squares of the diagonals is twice the sum of the squares of two adjascent sides. Also show that the difference of the squares on two adjacent sides is equal to the rectangle contained by either diagonal and the projection of the other upon it.

Prove that three times the sum of the squares on the sides of a triangle is equal to four times the sum of the square on the medians of the triangle.

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