因為

,所以

,則

。設向量

與

的夾角為

,則

,所以

,故選C
練習冊系列答案
相關習題
科目:高中數(shù)學
來源:不詳
題型:填空題
已知向量

,

滿足條件|

|=2,|

|=,且

與2

-

互相垂直,則

與

的夾角為_________。
查看答案和解析>>
科目:高中數(shù)學
來源:不詳
題型:填空題
自單位圓外任意一點

引圓的兩條切線,切點分別為點

、

,那么

的最小值是
.
查看答案和解析>>
科目:高中數(shù)學
來源:不詳
題型:單選題
已知點

,向量

,若

,則實數(shù)

的值為( )
A. | B. | C.1 | D.2 |
查看答案和解析>>
科目:高中數(shù)學
來源:不詳
題型:填空題
已知

是非零向量,且夾角為

,則向量

的模為_____________.
查看答案和解析>>
科目:高中數(shù)學
來源:不詳
題型:填空題
已知二次函數(shù)

的圖像為開口向下的拋物線,且對任意

都有


.若向量

,

,則滿足不等式

的

取值范圍為
.
查看答案和解析>>
科目:高中數(shù)學
來源:不詳
題型:解答題
已知

,

與

夾角為

(Ⅰ)若

與

共線,求

(Ⅱ)若

與

垂直,求

.
查看答案和解析>>