共50条信息
与向量\( \overrightarrow{a}=\left(1,- \sqrt{3}\right) \)垂直的一个单位向量是\((\) \()\)
已知向量\(\overrightarrow{a}=(-1,2)\),\(\overrightarrow{b}=(2,-3)\),若向量\(\lambda \overrightarrow{a}+\overrightarrow{b}\)与向量\(\overrightarrow{c}=(-4,7)\)共线,则\(λ\)的值为________.
设向量\(\overrightarrow{a}=\left(\sin 15^{\circ},\cos 15^{\circ}\right) \)、\(\overrightarrow{b}=\left(\cos 15^{\circ},\sin 15^{\circ}\right) \),则向量\(\overrightarrow{a}+ \overrightarrow{b} \)与\(\overrightarrow{a}- \overrightarrow{b} \)的夹角为( )
\((2)\)若\(b=c·\cos A\),\(\triangle ABC\)的外接圆的半径为\(1\),求\(\triangle ABC\)的面积.
向量\(\overrightarrow{a}=(1,x+1),\overrightarrow{b}=(1-x,2),\overrightarrow{a}\bot \overrightarrow{b},\)则\(\left( \overrightarrow{a}+\overrightarrow{b} \right)\cdot \left( \overrightarrow{a}-\overrightarrow{b} \right)=\)______.
已知\(A\),\(B\)是圆\(O:x^{2}+y^{2}=16\)上的两个动点,且\(|AB|=4\),\(\overrightarrow{OC}=\dfrac{{5}}{{3}}\overrightarrow{OA}-\dfrac{{2}}{{3}}\overrightarrow{OB}\),若\(M\)是线段\(AB\)的中点,则\(\overrightarrow{OC}\cdot \overrightarrow{OM}=\)
已知平面向量\(\overrightarrow{a}=({{x}_{1}},{{y}_{1}})\),\(\overrightarrow{b}=({{x}_{2}},{{y}_{2}})\),若\(|\overrightarrow{a}|=2\),\(|\overrightarrow{b}|=3\),\(\overrightarrow{a}\cdot \overrightarrow{b}=-6\),则\(\dfrac{{{x}_{1}}+{{y}_{1}}}{{{x}_{2}}+{{y}_{2}}}\)的值为
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