
20.(12分)在三棱台ABC-A1B1C1中,△ABC是等边三角形,AB=2,AA1=A1B1=1,平面ABB1A1⊥平面ABC,∠A1AC=90°.
(1)证明:AA1⊥平面ABC;
(2)点D在棱CC1上,直线BD与平面ACC1A1所成角的正切值为√6,求二面角A1-AB-D的余弦值.
作者:网络 来源: 2022-05-17 11:18:29 阅读:次
20.(12分)在三棱台ABC-A1B1C1中,△ABC是等边三角形,AB=2,AA1=A1B1=1,平面ABB1A1⊥平面ABC,∠A1AC=90°. (1)证明:AA1⊥平面ABC; (2)点D在棱CC1上,直线BD与平面ACC1A1所
20.(12分)在三棱台ABC-A1B1C1中,△ABC是等边三角形,AB=2,AA1=A1B1=1,平面ABB1A1⊥平面ABC,∠A1AC=90°.
(1)证明:AA1⊥平面ABC;
(2)点D在棱CC1上,直线BD与平面ACC1A1所成角的正切值为√6,求二面角A1-AB-D的余弦值.