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\(\overset{\to }{{{AD}}}\,\bullet \overset{\to }{{{BC}}}\,\)\(=\).
在\(\triangle ABC\)中,\(D\)是\(BC\)的中点,\(E\)是\(AD\)的中点,那么下列各式中错误的是( )
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\(\overset{}{{BE}}{⋅}\overset{}{{AC}}{=}\)__________.
若非零向量\(\overrightarrow{AB}\)与\(\overrightarrow{AC}\)满足\((\dfrac{\overrightarrow{AB}}{|\overrightarrow{AB}|}+\dfrac{\overrightarrow{AC}}{|\overrightarrow{AC}|})\bullet \overrightarrow{BC}=0\),且\(\dfrac{\overrightarrow{AB}}{|\overrightarrow{AB}|}\bullet \dfrac{\overrightarrow{AC}}{|\overrightarrow{AC}|}=\dfrac{1}{2}\),则\(\Delta ABC\)为\((\) \()\)
在\(\triangle ABC\)中,\(\left| \overrightarrow{AB}+\overrightarrow{AC} \right|=\sqrt{3}\left| \overrightarrow{AB}-\overrightarrow{AC} \right|,\left| \overrightarrow{AB} \right|=\overrightarrow{\left| AC \right|}=3\),则\(\overrightarrow{CB}\cdot \overrightarrow{CA}\)的值为( )
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
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