In a rectangle ABCD, M and N are the midpoints of the sides BC and CD respectively. If ˆANM=900 then AB:BC is
ABCD is a rectangle formed by the points A(-1, -1), B(-1, 4), C(5, 4) and D(5, -1). If P,Q,R and S be the midpoints of AB, BC, CD and DA respectively, show that PQRS is a rhombus.