Question

长方形ABCD-A'B'C'D'中，AB=BC=4, AA'=6, E

Answer 1

设A为(0,0,0),B(4,0,0),C(4,4,0),D(0,4,0),A'(0,0,6) 则：F坐标为(4,4,3) 所以AB=(4,0,0) , BF=(0,4,3) cos(AB,BF)=(AB)*(BF)/(|AB|*|BF|)=0 所以AB,BF所成角的余玄值为0