The coordinates of parallelogram ABCD are A(0, 0), B(a, 0), C( , ), and D(c, b). The coordinates of the midpoint of AC¯¯¯¯¯ are ( ,b2). The coordinates of the midpoint of BD¯¯¯¯¯ are (a+c2, ). The midpoints of the diagonals have the same coordinates. Therefore, AC¯¯¯¯¯ and BD¯¯¯¯¯ bisect each other.