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问题 选择题

△ABC是直径为10cm的⊙O的内接等腰三角形，如果此等腰三角形的底边BC=8cm，则该△ABC的面积为（　　）

A．8cm2

B．12cm2

C．12cm2或32cm2

D．8cm2或32cm2

答案

当△ABC在圆心的同侧时，根据弦心距，弦的一半和半径构造的直角三角形中的勾股定理可得出高为2，故面积为8；

当△ABC不在圆心的同侧时，根据弦心距，弦的一半和半径构造的直角三角形中的勾股定理可得出高为8，故面积为32．

所以△ABC的面积为8cm2或32cm2．

故选D．

单项选择题

At the time friends visit us in the evening, they often tell us they are in a hurry and look at their watches. It isn’t that our friends are all very busy; it is just that we haven’t got a television. People think that we are very strange. "But what do you do in the evening", they are always asking. The answer is very simple. Both my wife and I have hobbies. We certainly don’t spend our evenings looking at the walls. My wife enjoys cooking and painting and often attends evening classes in foreign languages. This is quite useful as we often go abroad for our holidays. I collect stamps and I’m always busy with my collection. Both of us enjoy listening to the music and playing chess together.
Sometimes there are power cuts and we have no electricity in the house. This does not worry us and we just light candles and carry on with what we were doing before. Our friends, however, are lost—no television! —So they don’t know what to do. On such evenings our house is very full for they all come to us. They all have a good time. Instead of sitting in silence in front of the television, everybody talks and plays games.

At night when there is no electricity, the couple ______.

A．have to look at the walls

B．can do nothing but sit in silence
C．will have many visitors

D．have to go out for candles
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多项选择题

云计算的关键技术（）。

A、虚拟化

B、服务计算

C、效用计算

D、可靠性计算
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