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

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

prove by vector method that the sum of the squares of the diagonals of a parallelogram is equal to the sum of the squares of its sides.

Prove by vector method that the sum of the square of the diagonals of a parallelogram is equal to the sum of the squares of its sides.

Prove analytically that the sum of square of the diagonals of a rectangle is equal to the sum of squares of its sides.

(Pythagoras's Theorem) Prove by vector method that in a right angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.

(Pythagoras's Theorem) Prove by vector method that in a right angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.