共50条信息
对于四面体\(ABCD\),给出下列四个命题:
\(①\)若\(AB=AC\),\(BD=CD\),则\(BC⊥AD\);\(②\)若\(AB=CD\),\(AC=BD\),则\(BC⊥AD\);
\(③\)若\(AB⊥AC\),\(BD⊥CD\),则\(BC⊥AD\);\(④\)若\(AB⊥CD\),\(AC⊥BD\),则\(BC⊥AD\).
其中为真命题的是\((\) \()\)
在正三棱柱\(ABC-{{A}_{1}}{{B}_{1}}{{C}_{1}}\)中,\(AB=\sqrt{2}B{{B}_{1}}\),则\(A{{B}_{1}}\)与\(B{{C}_{1}}\)所成角的大小为( )
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