共50条信息
向量\(a,b\)在正方形网格中的位置如图所示\(.\)如果小正方形网格的边长为\(1\),那么\(a\cdot b=\)____.
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\(\overset{}{{BE}}{⋅}\overset{}{{AC}}{=}\)__________.
如图,在\(\Delta ABC\)中,\(\overrightarrow{CD}=2\overrightarrow{DB}.\)若\(\overrightarrow{AD}=x\overrightarrow{AC}+y\overrightarrow{BC}(x,y\in R)\),则\(x-3y\)的值为________.
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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