题目

如图，已知圆上两点A，B．（1）用直尺和圆规求作圆心（保留作图痕迹，不写画法）；（2）若AB=6，此圆的半径为2，求弦AB与劣弧AB所组成的弓形面积． 答案：【答案】（1）见解析；（2）4π﹣3；【解析】（1）任意作出不同于AB的弦，然后作出弦AB、AC的垂直平分线，相交于点O，则点O即为所求；（2）由OD⊥AB，勾股定理计算出OD，这样可得到∠AOB=120°，而S弓形AB=S扇形OAB-S△AOB，然后利用扇形和三角形的面积公式计算即可．（1）如图所示，点O即为所求；（2）According to a new survey, students' safety has become a big problem. Now in some cities of China, many schools start a new lesson: self-protection. Students like this lesson because there are no exams or boring classes. And they can learn how to save lives and know how to stop danger before it really happens.Lin Li, a teacher from Yancheng, gives young students some advice on how to deal with danger.If you are in a traffic accidentIf a car hits you , you should remember the car number. If it is a bicycle, try to call your parents before you let the rider go. This is because you don't know how seriously you are hurt.If it is raining hard and there is lightningDon't stay in high places and stay away from trees.When there is a fireGet away as fast as you can. Put wet things on your body and try to find an exit. Don't take the lift.If someone drowningIf you can't swim, don't get into water. Cry out for help.Remember that danger is never as far away as you think. Take care of yourself at all times !If you are robbed.Keep calm. If you can not cry for help or run away, give the robber your money. Try to remember what         the robber looks like and tell the police later.根据文章内容，完成下列表格。Best title: How to deal with    小题1:DangerWhat to doTraffic   小题2:If hit by a car, you’re supposed to remember the car 小题3:  .If hit by a bike, call your   小题4: .Raining with lightningStay at 小题5:  places and keep away from trees小题6:Don’t take the lift and find an exit as fast as   小题7:DrowningIf you can’t swim , just shout “ 小题8:  !”RobberyKeep  小题9:Remember the robber’s  小题10:  and tell the police later.