题目

已知圆和两点，若圆上存在点，使得，当的最大值为6时，=________； 答案：【答案】.【解析】首先设，根据得到，即，再根据的最大值即可求出的值.由题知：圆.设，，，因为，所以.即.因为，且的最大值为.所以.即，解得.故答案为：Everyone has got two personalities(性格)—the one that is shown to the world and the other that is secret and real. You don’t show your secret personality when you’re awake because you can control your behavior, but when you’re asleep, your sleeping position shows the real you. In a normal night, of course, people frequently change their position. The important position is the one that you go to sleep in. If you go to sleep on your back, you’re a very open person. You normally trust people and you are easily influenced by fashion or new ideas. You don’t like to upset people, so you never express your real feelings. You’re quite shy and you aren’t very confident. If you sleep on your stomach, you are a rather secretive(不坦率的)person. You worry a lot and you’re always easily upset. You’re very stubborn, but you aren’t very ambitious(有雄心的). You usually live for today not for tomorrow. This means that you enjoy having a good time. If you sleep curled up(卷曲), you are probably a very nervous person. You have a low opinion of yourself and so you’re often defensive（提防的）. You’re shy and you don’t normally like meeting people. You prefer to be on your own. You’re easily hurt. If you sleep on your side, you have usually got a well-balanced personality. You know your strengths and weaknesses. You’re usually careful. You have a confident personality. You sometimes feel anxious, but you don’t often get depressed（压抑）. You always say what you think even if it annoys people.（words: 278） 1.According to the writer，you naturally show your secret and real personality _______. A．only in a normal night B．only when you go to sleep C．only when you refuse to show yourself to the world D．only when you change sleeping position 2.Which is NOT mentioned in the second paragraph about a person’s personality? A．He or she is always open with others. B．He or she always likes new ideas earlier than others. C．He or she is always easily upset. D．He or she tends（倾向） to believe in others. 3.Point out which sentence is used to show the personality of a person who is used to sleeping on his or her stomach? A．He or she is careful not to offend（冒犯） others. B．He or she doesn’t want to stick to his or her opinion. C．He or she likes to bring others happiness. D．He or she can’t be successful in any business. 4.Maybe you don’t want to make friends with a person who sleeps curled up. Why? A．He or she would rather be alone than communicate with you. B．He or she is rarely ready to help you. C．He or she prefers staying at home to going out. D．He or she wouldn’t like to get help from you. 5.It appears that the writer tends to think highly of the person who sleeps on one side because __________. A．he or she always shows sympathy for people B．he or she is confident，but not stubborn C．he or she has more strengths than weaknesses D．he or she often considers annoying people