q21406
幼苗
共回答了25个问题采纳率：92% 举报
(2)∵BB1⊥面ABC,∴BB1⊥AB
∵A1B1∥AB,∴BB1⊥A1B1
∵BB1⊥B1C1,∴BB1⊥面A1B1C1,∴面ABC∥面A1B1C1
连接A1E,易证四边形A1EBB1是平行四边形
∴A1E∥BB1∥CC1
∴A1,E,C,C1共面
∵面A1ECC1∩面A1B1C1=A1C1,面A1ECC1∩面ABC=CE
∴A1C1∥CE
∵AC=BC,∴CE⊥AB
又∵BB1⊥CE,∴C1⊥面AA1B1B,∴A1C1⊥面AA1B1B
1年前
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