In the parallelogram ABCD, 2Ab = ad, angle B = 60 degrees, m and N are the midpoint of AD and BC respectively, are Mn and AC perpendicular to each other? Why? Urgent!

In the parallelogram ABCD, 2Ab = ad, angle B = 60 degrees, m and N are the midpoint of AD and BC respectively, are Mn and AC perpendicular to each other? Why? Urgent!

Let AE intersect BC at point n, BF intersect ad at point m, connect nm, because ad = 2Ab, and because EC = CD = DF, DF = AB, triangle ABM is congruent with triangle DFM, similarly, triangle ABN is congruent with triangle ECN, because ad = BC, so 1 / 2ad = 2 / 1BC, so am = BN = AB, because ad is parallel to BC, so quadrilateral abnm is diamond, so AE is perpendicular to BF