精英家教网 > 高中数学 > 题目详情
已知,点C在内, ,若=2m+m),则=(    )                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
A.1B.2C.D.4
D

试题分析:根据题意,由于,点C在内, ,若=2m+m),那么两边同时乘以,结合向量的夹角和模长公式,和数量积为零得到参数k的值为4,故选D.
点评:主要是考查了向量的数量积的运算,以及向量的垂直的充要条件的运用,属于基础题。
练习册系列答案
相关习题

科目:高中数学 来源:不详 题型:解答题

已知,且的夹角为120°.
求:(1)  ;         (2) ;       (3) .

查看答案和解析>>

科目:高中数学 来源:不详 题型:填空题

如图所示,向量在一条直线上,且,则__________________(用表示)

查看答案和解析>>

科目:高中数学 来源:不详 题型:填空题

已知,坐标原点上的射影为点,则      .

查看答案和解析>>

科目:高中数学 来源:不详 题型:解答题

在△ABC中,,记,△ABC的面积为,且满足.
(1)求的取值范围;
(2)求函数的最大值和最小值.

查看答案和解析>>

科目:高中数学 来源:不详 题型:解答题


(Ⅰ)若,求实数的值;
(Ⅱ)求方向上的正射影的数量.

查看答案和解析>>

科目:高中数学 来源:不详 题型:单选题

已知向量,且,则m等于(   )
A.2B.C.D.

查看答案和解析>>

科目:高中数学 来源:不详 题型:单选题

在梯形ABCD中,AD//BC,对角线ACBD,且AC=12,BD=9,则此梯形的
中位线长是( ).
A.B.C.D.

查看答案和解析>>

科目:高中数学 来源:不详 题型:单选题

已知
A.B.C.D.

查看答案和解析>>

同步练习册答案