共50条信息
如图所示,空间四边形\(OABC\)中,\(\overrightarrow{OA}=a\),\(\overrightarrow{OB}=b\),\(\overrightarrow{OC}=c\),点\(M\)在\(\overrightarrow{OA}\)上,且\(\overrightarrow{OM}=2\overrightarrow{MA}\),\(N\)为\(BC\)的中点,\(\overrightarrow{MN}=xa+yb+zc\),则\(x\),\(y\),\(z\)分别为
对于空间中的三个向量\(a\),\(b\),\(2a-b.\)它们一定是( )
如图所示,在平行六面体\(ABCD-A_{1}B_{1}C_{1}D_{1}\)中,设\( \overrightarrow{A{A}_{1}}= \overrightarrow{a} \),\( \overrightarrow{AB}= \overrightarrow{b} \),\( \overrightarrow{AD}= \overrightarrow{c} \),\(M\),\(N\),\(P\)分别是\(AA_{1}\),\(BC\),\(C_{1}D_{1}\)的中点,则\( \overrightarrow{MP}+ \overrightarrow{N{C}_{1}}= =(\) \()\)
三棱柱\(ABC-{{A}_{1}}{{B}_{1}}{{C}_{1}}\)中,若\(\overrightarrow{CA}=\overrightarrow{a},\overrightarrow{CB}=\overrightarrow{b},\overrightarrow{C{{C}_{1}}}=\overrightarrow{c}\),则\(\overrightarrow{{{A}_{1}}B}=\)
已知\(\overrightarrow{a}=(2,4,5)\),\(\overrightarrow{b}=(3,x,y)\)分别是直线\(l_{1}\)、\(l_{2}\)的方向向量\(.\)若\(l_{1}/\!/l_{2}\),则\((\) \()\)
已知在正方体\(ABCD-{{A}_{1}}{{B}_{1}}{{C}_{1}}{{D}_{1}}\)中,侧面\(C{{C}_{1}}{{D}_{1}}D\)的中心是\(F\),若\(\overrightarrow{AF}=\overrightarrow{AD}+m\overrightarrow{AB}+n\overrightarrow{A{{A}_{1}}}\),则\(m+n=(\) \()\)
如图\(P\)为空间中任意一点,动点\(Q\)在\(\triangle ABC\)所在平面内运动,且\( \overset{⇀}{PQ}=2 \overset{⇀}{PA}-3 \overset{⇀}{PB}+m \overset{⇀}{CP} \),则实数\(m=\)( )
如图,在四面体\(A\)\(\)\(BCD\)中,已知\( \overrightarrow{AD}= \overrightarrow{a}, \overrightarrow{AB}= \overrightarrow{b}, \overrightarrow{AC}= \overrightarrow{c}, \overrightarrow{BE}= \dfrac{1}{2} \overrightarrow{EC} \),则\( \overrightarrow{DE} \)等于( )
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