共50条信息
称\(d(a,b)=|a-b|\)为两个向量\(a\),\(b\)间的“距离”\(.\)若向量\(a\),\(b\)满足:\(①|b|=1\);\(②a\neq b\);\(③\)对任意的\(t∈R\),恒有\(d(a,tb)\geqslant d(a,b)\),则( )
已知\(\triangle ABC\)是单位圆的内接三角形,\(AB=AC=1\),过点\(A\)作\(BC\)的垂线交单位圆于点\(D\),则\(\overrightarrow{{AB}}·\overrightarrow{{CD}}=\)____\(.\)
若向量\(\vec{a}=(1,\lambda ,2),\vec{b}=(2,-1,2)\),且\(\vec{a}\)与\(\vec{b}\)的夹角余弦为\(\dfrac{8}{9}\),则\(\lambda \)等于\((\) \()\)
若\(A(1,-2,1)\),\(B(4,2,3)\),\(C(6,-1,4)\),则\(\triangle ABC\)的形状是\((\) \()\)
空间四边形\(OABC\)中,\(OB=OC\),\(\angle AOB=\angle AOC=\dfrac{\pi }{3}\),则\(\cos < \overrightarrow{OA},\overrightarrow{BC} > \)的值是\((\) \()\)
若向量\(\vec{a}=2\vec{i}-\vec{j}+\vec{k},\vec{b}=4\vec{i}+9\vec{j}+\vec{k},\),则这两个向量的位置关系是___________。
已知向量\( \overrightarrow{a}=\left(0,-1,1\right) \),\( \overrightarrow{b}=\left(4,1,0\right) \),\(\left|λ \overrightarrow{a}+ \overrightarrow{b}\right|= \sqrt{29} \)且\(λ > 0 \),则\(λ= \)_______.
已知向量\(a=(1,-1)\),\(b=(1,2)\),向量\(c\)满足\((c+b)⊥a\),\((c-a)/\!/b\),则\(c\)等于( )
已知直线\(x+y=a\)与圆\({x}^{2}+{y}^{2}=4 \)交于\(A\)、\(B\)两点,且\(| \overset{⇀}{OA}+ \overset{⇀}{OB}|=| \overset{⇀}{OA}- \overset{⇀}{OB}| \),其中\(O\)为原点,则实数的值为\((\) \()\)
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