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.
句型转换填空。 |
1. He has never surfed, _____ _____ ? (改成反意疑问句) 2. They have been here since 2000. (对划线部分提问) _____ _____ have they been here? 3. The old man _____ last year. He _____ _____ _____ for a year. (die) (动词填空) 4. This factory opened twenty years ago.(同义句转换) This factory _____ _____ _____ for twenty years. 5. Miss Gao left an hour ago. (同义句转换) Miss Gao _____ _____ _____ an hour ago. 6. Her mother has been a Party member for three years .(同义句) Her mother _____ the Party three years_____ . 7. The Green Family moved to France two years ago. (同义句转换) _____ two years _____ the Green family moved to France. 8. The bus has arrived here. It arrived ten minutes ago. (把两个句子合并成一个句子) ______________________________________. |