问题
解答题
已知向量
(1)
(2)
|
答案
由已知
=(3,-2),a
=(4,1),b
(1)
•a
=3×4-1×2=10,b
|
+a
|=|(7,-1)|=b
=550
.2
(2)|
|=a
,|13
|=b
,17
∴cosθ=
=
•a b |
||a
|b 10 221 221
已知向量
(1)
(2)
|
由已知
=(3,-2),a
=(4,1),b
(1)
•a
=3×4-1×2=10,b
|
+a
|=|(7,-1)|=b
=550
.2
(2)|
|=a
,|13
|=b
,17
∴cosθ=
=
•a b |
||a
|b 10 221 221