Question

正方体AC'中,E、F分别是A‘D’与C’D‘中点.求证：EF⊥面B’BDD‘

Answer 1

略解

1 EF//A'C'

2 A'C'⊥DD'

3 A'C'⊥BD

4 A'C'⊥面B’BDD‘

5 EF⊥面B’BDD‘