E,F,G,E1,F1,G1分别是AD,AB,A1D1,A1B1C1D1的中点,求证：∠GEF=∠G1E1F1   打漏
 
应该是   E,F,G,E1,F1,G1分别是AD,AB,CD,A1D1,A1B1,C1D1的中点,求证：∠GEF=∠G1E1F1
 
E1F1＝D1B1/2＝GB/2＝EF﹙向量﹚ 
 
E1G1＝A1C1/2＝AC/2＝EG
 
∴∠G1E1F1＝∠GEF,﹙其实都是直角﹚