证明：连接A1B,在正方体ABCD-A1B1C1D1中,面A1B1BA是正方形,对角线A1B⊥AB1,在正方体ABCD-A1B1C1D1中,D1A1⊥面A1B1BA,AB1在面A1B1BA上,∴D1A1⊥AB1,∵AB1⊥A1B,AB1⊥D1A1,A1B和D1A1是面A1BD1内的相交直线,∴AB1⊥面A1...