若
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=
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,
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=
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,则
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在
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上的射影为________________.
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科目:高中数学
来源:不详
题型:解答题
(本小题满分7分)已知向量

,且满足

。
(1)求向量

的坐标; (2)求向量

与

的夹角。
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科目:高中数学
来源:不详
题型:解答题
(本小题满分

分)在平面直角坐标系中,已知两个定点
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和

.动点

在

轴上的射影是

(

随

移动而移动),若对于每个动点
M总存在相应的点

满足

,且

.
(Ⅰ)求动点

的轨迹

的方程;
(Ⅱ)设过定点

的直线

(直线

与

轴不重合)交曲线

于
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,
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两点,求证:直线

与直线

交点总在某直线

上.
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科目:高中数学
来源:不详
题型:解答题
已知⊙

的直径为10,

是⊙

的一条直径,长为20的线段

的中点

在⊙

上运动(异于

、

两点).
(Ⅰ)求证:

与点

在⊙

上的位置无关;
(Ⅱ)当

的夹角

取何值时,

有最大值.
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来源:不详
题型:单选题
已知单位向

量a,b 的夹角为

,则a+b的模是( )。
A.2 | B. | C. 1 | D.4 |
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科目:高中数学
来源:不详
题型:填空题
在△
ABC中,若

,

,则

的值为____________.
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