let PQRS be a quadrilateral . if M and N are the midpoints of the sides PQ and RS respectively then prove that PS- + QR- =2MN- here - means bar Share with your friends Share 0 Brijendra Pal answered this Dear Student, Let P = x,y Q =a,bR= m,nS =u,vSo PS+ QR = m-ai+n-bj+ u-xi+v-yj=m-a+u-xi+n+v-y-bj......1Now M = x+a2,y+b2 and N = m+u2,n+v2 MN =m+u2-x+a2 i+n+v2-y+b2j=12m+u-a-xi+12n+v-y-bjSo 2MN = m-a+u-xi+n+v-y-bj= PS+ QRUsing equation 1. Regards 3 View Full Answer