题目内容

已知
OA
=(1,1),
OB
=(4,1),
OC
=(4,5),则
AB
AC
夹角的余弦值为(  )
A.
4
5
B.
3
5
C.0D.以上结果都不对
AB
=
OB
-
OA
=(4,1)-(1,1)=(3,0),
AC
=
OC
-
OA
=(4,5)-(1,1)=(3,4).
AB
AC
=(3,0)•(3,4)=9
cos<
AB
AC
=
AB
AC
|
AB
||
AC
|
=
9
32+42
=
3
5

故选:B.
练习册系列答案
相关题目

违法和不良信息举报电话:027-86699610 举报邮箱:58377363@163.com

精英家教网