问题
填空题
设F1，F2为椭圆
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答案
由题意知∠AF2F1 小于45°，故 tan∠AF2F1 ;=
＜1，即 |AF1| |F1F2|
＜1，b2 a 2c
b2＜2ac，a2-c2＜2ac，e2+2e-1＞0，∴e＞
-1，或 e＜-1-2
（舍去）．2
又 0＜e＜1，故有
-1＜e＜1，2
故答案为：
-1＜e＜1．2
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设F1，F2为椭圆
|
由题意知∠AF2F1 小于45°，故 tan∠AF2F1 ;=
＜1，即 |AF1| |F1F2|
＜1，b2 a 2c
b2＜2ac，a2-c2＜2ac，e2+2e-1＞0，∴e＞
-1，或 e＜-1-2
（舍去）．2
又 0＜e＜1，故有
-1＜e＜1，2
故答案为：
-1＜e＜1．2
| 完形填空。 One day a great general ( * * ) asked his soldiers, "What's the strongest power in the world?" Four of his soliders 1 their hands. They all wanted to answer the question. The general asked the first man to speak. The first man is younger 2 the other three, and he was not strong. He said, "My gun is the strongest. It can kill 3 ." "Thank you. 4 , please."The second man was very strong. He said,"I don't 5 . Soldiers use guns, so the soldier is the strongest."The 6 man said, "Soldiers use guns, 7 our general gives orders (命令).So I think our general is the strongest."The fourth man was the 8 . He said, "Love is the strongest. For love people don't 9 guns."The general smiled and 10 to him. | ||||
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