Complete the coordinate proof of the theorem. given: abcd is a parallelogram. prove: the diagonals of abcd bisect each other. the coordinates of parallelogram abcd are a(0, 0) , b(a, 0) , c(a+c, b) , and d( , ). the coordinates of the midpoint of ac are ( a+c2 , ). the coordinates of the midpoint of bd are ( , b2 ). the midpoints of the diagonals have the same coordinates. therefore, the diagonals of abcd bisect each other.