问题
选择题
平面上O,A,B三点不共线,设
|
答案
S△OAB=
|1 2
||a
|sin<b
,a
>b
=
|1 2
||a
|b 1-cos2<
,a
>b
=
|1 2
||a
|•b 1- (
•a
)2b |
|2|a
|2b
=1 2
;|
|2|a
|2-(b
•a
)2b
故选C.
平面上O,A,B三点不共线,设
|
S△OAB=
|1 2
||a
|sin<b
,a
>b
=
|1 2
||a
|b 1-cos2<
,a
>b
=
|1 2
||a
|•b 1- (
•a
)2b |
|2|a
|2b
=1 2
;|
|2|a
|2-(b
•a
)2b
故选C.