(1)BD⊥AC
BD⊥CC1
BD⊥面ACC1
BD⊥AC1
(2)连接AB1,交A1B于O
AO⊥A1B
D1A1⊥面ABB1A1
AO⊥D1A1
AO⊥面A1BD
AO即为点A到平面A1BD的距离(AO很好算了吧)