共50条信息
三棱锥\(A-BCD\)中,\(AB=AC=AD=2\),\(∠BAD=90^{\circ}\),\(∠BAC=60^{\circ}\),则\(\overrightarrow{AB}\)\(·\)\(\overrightarrow{CD}\)等于\((\) \()\)
如图,在三棱柱\(ABC-A_{1}B_{1}C_{1}\)中,\(M\)为\(A_{1}C_{1}\)的中点,若\(\overrightarrow{AB}=\overrightarrow{a}\),\(\overrightarrow{BC}=\overrightarrow{b}\),\(\overset{⇀}{A{A}_{1}}= \overset{⇀}{c} \),则\(\overrightarrow{BM}\)可表示为\((\) \()\)
在平行六面体\(ABCD-A_{1}B_{1}C_{1}D_{1}\) 中,设\( \overrightarrow{A{C}_{1}}=x \overrightarrow{AB}+2y \overrightarrow{BC}+3z \overrightarrow{C{C}_{1}} \),则\(x{+}y{+}z=(\) \()\)
如图所示,空间四边形\(OABC\)中,\(\overrightarrow{OA}=a\),\(\overrightarrow{OB}=b\),\(\overrightarrow{OC}=c\),点\(M\)在\(OA\)上,且\(OM=2MA\),点\(N\)为\(BC\)的中点,则\(\overrightarrow{MN}\)等于\((\) \()\)
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