设四棱柱ABCD-A1B1C1D1,A1C1∩B1D1=O1,设菱形两条对角线第分别为m,n,菱形边长为a,因为侧面是矩形,故四棱柱是直棱柱,设棱柱高为h,Q1=mh,m=Q1/h,Q2=nh,n=Q2/h,∵A1C1⊥B1D1,∴根据勾股定理,（m/2)^2+(n/2)^2=a^2,a=(1/...