证明:(1)连接AC1交A1C于点E,连接DE
∵四边形AA1C1C是矩形,则E为AC1的中点
又∵D是AB的中点,DE∥BC1,
又DE?面CA1D,BC1?面CA1D,
∴BC1∥平面CA1D;
(2)AC=BC,D是AB的中点,
∴AB⊥CD,
又∵AA1⊥面ABC,CD?面ABC,
∴AA1⊥CD,
∵AA1∩AB=A,
∴CD⊥面AA1B1B,
又∵CD?面CA1D,
∴平面CA1D⊥平面AA1B1B
(3)则由(2)知CD⊥面ABB1B,
∴三棱锥B1-A1DC底面B1A1D上的高就是CD=
,
3
又∵BD=1,BB1=
,
3
∴A1D=B1D=A1B1=2,SA1B1D=
,
3
∴三棱锥B1-A1DC的体积VB1?A1DC=VC?A1B1D=
?1 3
?
3
=1
3