问题 选择题

下列命题中是假命题的是( )

A.直径是弦;

B.等弧所在的圆是同圆或等圆

C.弦的垂直平分线经过圆心;

D.平分弦的直径垂直于弦

答案

答案:D

考点:

分析:根据直径的定义、等弧的定义、垂径定理的推论分别进行判断.

解答:解:A、直径是过圆心的弦,故本选项正确;

B、能完全重合的弧叫等弧,因此只有在同圆或等圆中才有等弧,故本选项正确;

C、弦的垂直平分线经过圆心,故本选项正确;

D、平分(非直径)弦的直径垂直于弦,故本选项错误.

故选D.

点评:本题考查了垂径定理:垂直于弦的直径平分弦,并且平分弦所对的弧.也考查了垂径定理的推论:弦的垂直平分线必过圆心;平分(非直径)弦的直径垂直弦,并且平分弦所对的弧以及有关圆的知识.

阅读理解

任务型阅读。

Quick Work

     Ted Robinson has been worried all the week. Last Tuesday he

received a letter from the local police station. In the letter he was asked

to call at the station. Ted wondered why he was wanted by the police,

but he went to the station yesterday and he is not worried any more.

     At the station, he was told by a smiling policeman that his bicycle

had been found. Five days ago, the policeman told him, the bicycle was

picked up in a small village four hundred miles away. It is now being sent to his home by train.

    Ted was most surprised when he heard the news. He was happy, too, because he never expected the bicycle to be found. It was stolen twenty years ago when Ted was a boy of fifteen.

1. What happened last Tuesday?

                                                                                  

2. What was he told at the station?

                                                                                

3. What are the police doing with the bicycle?

                                                                                

4. Why was he surprised and happy?

                                                                                

5. How old was Ted when his bicycle was stolen?

                                                                                  

填空题