Two pairs of opposite angles are equal in measure. The diagonals bisect each other. ... The sum of the squares of the sides equals the sum of the squares of the diagonals. (This is the parallelogram law.)
Two pairs of opposite angles are equal in measure. The diagonals bisect each other. The sum of the squares of the sides equals the sum of the squares of the diagonals. (This is the parallelogram law.)
