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问题 填空题
F1、F2是双曲线
x2
4a2
-
y2
a2
=1(a＞0)的两个焦点，P为双曲线上一点，
PF1
•
PF2
=0，且△F1PF2的面积为1，则a的值是______．
答案

∵F1、F2是双曲线

x2
4a2
-
y2
a2
=1(a＞0)的两个焦点，

设双曲线的点P到两个焦点的距离分别是m，n

∴根据双曲线的定义知m-n=4a，①

∵P为双曲线上一点，

PF1
•
PF2
=0，

∴m2+n2=20a2  ②

把①平方减去②得，mn=2a2，

∵△F1PF2的面积为1，

∴

1
2
×2a2=1

∴a=1

故答案为：1

阅读理解

阅读理解。

     I am Cathy Brown.   I am from America.   I am working for the  Sunshine Travel  Agency(旅行社) in Changsha now.     Last week I took a group of French holiday-makers for a week’s trip to Taiwan.    We traveled all around the island(岛).   It is very beautiful.   There are a lot of places of interest.   My favorite place is the Sun and Moon Lake. You may ask why people call it so.   If you fly high up over the lake and look down from your plane,    you will find the answer yourself.   In the middle of this lake, there is a small island. People call it the Pearl Island(珍珠岛) because it looks like a pearl.On one side of the Pearl Island, the lake looks like a sun, and on the other side, it looks like a moon. That is why people call it the Sun and Moon Lake.There are many mountains around the Sun and Moon Lake.   One of the most famous ones is the Ali Mountain. We stayed there for three days. We also had a dance party with Gaoshan people.   On our first day there, we watched the sun going down slowly in the west.  On our last day, we got up early   and saw a very beautiful sunrise(日出).Taiwan is a wonderful place to visit.

根据短文内容，判断下列句子正（T）误（F）。  

(    )1.Cathy went to Taiwan with some Americans last week.

(    )2.Cathy thinks Taiwan is a beautiful place with lots of places of interest.

(    )3.The Sun and Moon Lake gets its name because it looks like the sun during the day and looks like

the moon at night.

(    )4.Ali Mountain is near the Sun and Moon Lake.

(    )5.Cathy watched the sun going up and going down on different days.
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单项选择题

《预算法》规定，经本级政府财政部门批复的部门预算、决算及报表，应当在批复后（）内由各部门向社会公开，并对部门预算、决算中机关运行经费的安排、使用情况等重要事项作出说明。

A.五日

B.十日

C.二十日

D.二十五日
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