题目
题型:不详难度:来源:
π |
6 |
π |
2 |
3 |
CA |
CB |
CM |
A.1 | B.-1 | C.
| D.-
|
答案
π |
6 |
π |
2 |
3 |
所以|BC|=|AC|tan∠A=
3 |
| ||
3 |
又因为M是AB的中点,所以
CM |
1 |
2 |
CA |
CB |
故(
CA |
CB |
CM |
CA |
CB |
1 |
2 |
CA |
CB |
=
1 |
2 |
CA |
CB |
1 |
2 |
故选A
核心考点
试题【在△ABC中,∠A=π6,∠C=π2,|AC|=3,M是AB的中点,那么(CA-CB)•CM=( )A.1B.-1C.3D.-3】;主要考察你对平面向量数量积的运算等知识点的理解。[详细]
举一反三
a |
b |
a |
b |
A.(1,1,1) | B.0 | C.-2 | D.(0,0,-2) |
x2 |
2 |
y2 |
b2 |
3 |
PF1 |
PF2 |
A.-12 | B.-2 | C.0 | D.4 |
a |
i |
i |
k |
b |
i |
j |
k |
a |
b |
A.-1 | B.-3 | C.-5 | D.-15 |
PA |
PB |
PB |
PC |
PC |
PA |
A.-
| B.-
| C.-
| D.-
|