若，且，則向量與的夾角為（    ）
Ａ．30⁰   B．60⁰    Ｃ．120⁰  Ｄ．150⁰

已知向量，,若，則的值為（    ）                                                 

A．

B．

C．

D．

已知，，，點(diǎn)C在內(nèi)， ，若=2m+m（），則=（    ）                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         

A．1

B．2

C．

D．4

設(shè)、、為非零向量，且++=，向量、夾角為，，則向量與的夾角為     。

已知向量，若是等邊三角形，則的面積為                   .

非零向量，，，若向量，則的最大值為（   ）

A．

B．

C．

D．以上均不對(duì)

已知以為直徑的半圓，圓心為，為半圓上任意點(diǎn)，在線段上，則的最小值是（   ）

A．

B．

C．

D．

在△ABC中，，記，△ABC的面積為，且滿足.
（1）求的取值范圍；
（2）求函數(shù)的最大值和最小值.

已知向量，，若，則的最小值為             .

已知向量滿足，滿足，，若與共線，則的最小值為（    �。�

A．

B．

C．

D．