题目

(本题满分12分) 如图，已知AB是⊙O的直径，点C在⊙O上，过点C的直线与AB的延长线交于点P，AC=PC，∠COB=2∠PCB.  1.（1）求证：PC是⊙O的切线；   2.（2）求∠P的度数；   3.（3）点M是弧AB的中点，CM交AB于点N，AB=4，求线段BM、CM及弧BC所围成的图形面积。  答案： 1.（1）∵OA=OC,∴∠A=∠ACO       ∵∠COB=2∠A ,∠COB=2∠PCB               ∴∠A=∠ACO=∠PCB      ……………………………………………………1分           ∵AB是⊙O的直径   ∴∠ACO+∠OCB=90°        …………………………………………………2分          ∴∠PCB+∠OCB=90°,即OC⊥CP One of the most difficult problems a young person faces is deciding what to do．Some people，however, from the time they are six years old“know”that they want to be doctors or teachers or firefighters．but most of us do not get around to making a decision about a job until someone or something forces us to face the problem．Choosing a job takes time，and there are a lot of things you have to think about as you try to decide what you would like to do．You may find that you will have to take special courses for a particular kind of work，or you may find out that you will need to get enough knowledge for a particular job．Fortunately，there are a lot of people you can turn to for advice and help in making your decision．At most schools，there are teachers to give you information about jobs．And you can talk over your ideas with family members and friends who are always ready to listen and to offer suggestions．【1】In the first paragraph“get round to”means ________．A．consider B．go all the wayC．arrive at D．remain he same【2】The passage tells you that ________ for a particular job．A．you should have ideas when you are a childB．it’s impossible for you to get enough knowledgeC．you have to face the problemD．you may enter a class to study【3】Making a decision about your job ________．A．needs friends B．needs timeC．cost money D．cost your ability