题干

已知F1、F2分别是双曲线
x
2
a
2
y
2
b
2
=1(a>0,b>0)
的左右焦点,A为双曲线的右顶点,线段AF2的垂直平分线交双曲线与P,且|PF1|=3|PF2|,则该双曲线的离心率是(   )

A:3

B:2

C:1+172

D:1+172

上一题 下一题 0.0难度 选择题 更新时间:2014-04-09 10:19:29

答案(点此获取答案解析)

C

同类题1

任务型阅读

    What is the easiest way to stay warm in the super cold?____. At least that is what Santa Claus told me.

    During Christmas, Dennis and I went to Finland. We brought back some tips for keeping warm in a cold temperature.

    ⒈There layers(层)work wonders.

    Start with the base layer, which sits right on your skin: choose something that can absorb sweat____A sweater is a good choice. The most important layer is the outer clothes, which should be waterproof(防水的)and windproof.

    ⒉____.

    You lose heat from every millimeter of uncovered skin, which was the biggest lesson I learned on this trip. My whole body was well covered. But I missed one sport: my face. So it often felt like the wind was going to blow my nose off.

    ⒊Exercise, don't just stand still.

    When it's cold, exercising may be the last thing you feel like doing, but be smart.____and you will feel the difference. When we first got to Finland, we were freezing. But after a couple of minutes jumping around, we felt less cold.

    ⒋If you have a heater

    You may want to turn it all the way up, but it's best to keep it at between 18 and 20 degrees____but not create a huge difference between inside and outside.

A. Grow a crazy beard.

B. The key is what your layer is

C. Cover every bit of your skin

D. That will keep you comfortable

E. Take a walk, faster than your normal speed

F. Don't forget to keep your hands and feet warm, too

G. The middle layer keeps your body heat from getting away