共50条信息
在\(\Delta ABC\)中,\(\angle BAC=120{}^\circ ,AB=2,AC=1,D\)是边\(BC \)上一点,\(DC=2BD, \)则\(\overset{\to }{{{AD}}}\,\bullet \overset{\to }{{{BC}}}\,\)\(=\).
如图,在\({ΔABC}\)中,已知\({∠}BAC{=}\dfrac{\pi}{3}\),\(AB{=}2\),\(AC{=}3\),\(\overset{}{{DC}}{=}2\overset{}{{BD}}\),\(\overset{}{{AE}}{=}3\overset{}{{ED}}\),则\(\overset{}{{BE}}{⋅}\overset{}{{AC}}{=}\)__________.
在平行四边形\(ABCD\)中,\(\overrightarrow{AB}=\overrightarrow{a}\),\(\overrightarrow{AC}=\overrightarrow{b}\),\(\overrightarrow{NC}= \dfrac{1}{4}\overrightarrow{AC}\),\(\overrightarrow{BM}= \dfrac{1}{2}\overrightarrow{MC}\),则\(\overrightarrow{MN}=\)________\((\)用\(\overrightarrow{a}\),\(\overrightarrow{b}\)表示\()\).
设\(\overset{\to }{{a}}\,\),\(\overset{\to }{{b}}\,\)都是非零向量,下列四个条件中,能使\(\dfrac{\overrightarrow{a}}{|\overrightarrow{a}|}=\dfrac{\overrightarrow{b}}{|\overrightarrow{b}|}\)成立的是
已知\(\Delta ABC\)是边长为\(2\)的等边三角形,\(P\)为平面\(ABC\)内一点,则\((\overrightarrow{PB}-\overrightarrow{AB})\cdot (\overrightarrow{PB}+\overrightarrow{PC})\)的最小值是\((\) \()\)
已知\({{A}_{1}}\),\({{A}_{2}}\),\({{A}_{3}}\)为平面上三个不共线的定点,平面上点\(M\)满足\( \overrightarrow{{A}_{1}M}=λ\left( \overrightarrow{{A}_{1}{A}_{2}}+ \overrightarrow{{A}_{1}{A}_{3}}\right) (\lambda \)是实数\()\),且\( \overrightarrow{M{A}_{1}}+ \overrightarrow{M{A}_{2}}+ \overrightarrow{M{A}_{3}} \)是单位向量,则这样的点\(M\)有\((\) \()\)
已知菱形的边长为,,点,分别在边、上,\(\overrightarrow{DC}=2\overrightarrow{DF},\overrightarrow{BE}=\lambda \overrightarrow{CE}.\)若\(\overrightarrow{AE}\cdot \overrightarrow{AF}=1\),则实数的值为 .
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