题目

小明把半径为1的光盘、直尺和三角尺形状的纸片按如图所示放置于桌面上，此时，光盘与AB，CD分别相切于点N，M．现从如图所示的位置开始，将光盘在直尺边上沿着CD向右滚动到再次与AB相切时，光盘的圆心经过的距离是 ． 答案：【考点】切线的性质；轨迹． 【专题】应用题；压轴题． 【分析】根据切线的性质得到OH=PH，根据锐角三角函数求出PH的长，得到答案． 【解答】解：如图，当圆心O移动到点P的位置时，光盘在直尺边上沿着CD向右滚动到再次与AB相切，切点为Q， ∵ON⊥AB，PQ⊥AB， ∴ON∥PQ， ∵ON=PQ，∴OH=PH， 在Rt△PHQ中When I was about 12, I had an enemy, a girl who liked to point out my shortcomings(缺点). Sometimes she said I was thin. Sometimes she said I was lazy. Sometimes she said I wasn’t a good student. Sometimes she said I talked too much, and so on. I tried to put up with(忍受) her as long as I could. At last, I became very angry. I ran to my father with tears in my eyes. He listened to me quietly, and then he asked, “Are the things she said true or not? Mary, didn’t you ever wonder what you’re really like? Go and make a list of everything she said and mark the points that are true. Pay no attention to the other things she said.” I did as he told me and to my surprise, I discovered that about half the things were true. I brought the list back to my dad. He refused to take it. “That’s just for you,” he said. “You know better than anyone else the truth about yourself. When something said about you is true, you’ll find it will be helpful to you. Don’t shut your ears. Listen to them all, but hear the truth and do what you think is right.” Many years have passed. The situation often appears in my mind. In our life we often meet with some trouble and we often go to someone and ask for advice. For some advice you will treasure(珍惜) all your life!【小题1】What did the writer’s father do after he heard her complaints(抱怨)?A．He agreed with her “enemy”.B．he let her continue to put up with her “enemy”.C．He told her to write down all her “enemy” had said about her.D．He told her not to pay attention to what her “enemy” had said.【小题2】The writer felt ______ when she did the things as her father had told her.A．surprisedB．angryC．disappointedD．sad【小题3】Which of the following can we know from the passage?A．The “enemy” thought the writer was pretty.B．The “enemy” thought the writer studied hard.C．The writer and her “enemy” became best friends at last.D．The writer is grateful to her father.【小题4】Which of the following can be the best title of the passage?A．My ParentsB．A Serious Criticism(批评)C．What People Say About You Is Always RightD．The Best Advice I Ever Had