已知如图10-22,斜三棱柱ABC-A1B1C1的侧面A1ACC1与底面ABC垂直,∠ABC=90°,
BC=2,AC=2,且AA1⊥A1C,AA1=A1C.
(Ⅰ)求侧棱A1A与底面ABC所成角的大小;
(Ⅱ)求侧面A1ABB1与底面ABC所成二面角的大小;
已知如图10-22,斜三棱柱ABC-A1B1C1的侧面A1ACC1与底面ABC垂直,∠ABC=90°,
BC=2,AC=2,且AA1⊥A1C,AA1=A1C.
(Ⅰ)求侧棱A1A与底面ABC所成角的大小;
(Ⅱ)求侧面A1ABB1与底面ABC所成二面角的大小;
解:如图10-54,(Ⅰ)作A1D⊥AC,垂足为D,由面A1ACC1⊥面ABC,得A1D⊥面ABC.
∴∠A1AD为A1A与面ABC所成的角.
∵AA1⊥A1C,AA1=A1C,
∴∠A1AD=45°为所求.
(Ⅱ)作DE⊥AB,垂足为E,连A1E,则由A1D⊥面ABC,得A1E⊥AB.
∴∠A1ED是面A1ABB1与面ABC所成二面角的平面角.
由已知,AB⊥BC,得ED∥BC又D是AC的中点,BC=2,AC=2,
∴DE=1,AD=A1D=,tg∠A1ED=
=
.
故∠A1ED=60°为所求.
(Ⅲ)作BF⊥AC,F为垂足,由面A1ACC1⊥面ABC,知BF⊥面A1ACC1.
∵B1B∥面A1ACC1,
∴BF的长是B1B和面A1ACC1的距离.
在Rt△ABC中,AB==2
,
∴BF==
为所求.