题目

尺规作图：如图，作一个角等于已知角．（要求：写出已知、求作，保留作图痕迹，不写作法）．已知：求作： 答案：【答案】见解析.【解析】首先画射线CF；再以O为圆心，任意长为半径画弧交OA、OB于E、D；以C为圆心，OD长为半径画弧，然后再以N为圆心ED长为半径画弧，交前弧于M，过M作射线AE可得∠ECF.已知：∠AOB，求作：∠ECF等于∠AOB，如图所示：∠ECF即为所求　　Dyson fixed the little box on Eva’s head． “It”s a very clever machine”, he said． “When a person tells a lie, this needle here moves round． The numbers 0 to 20 show the size of the lie． Now, tell me a few good lies．” 　　Eva laughed． “What about? I never tell lies!” 　　The needle moved from zero to 4． “You’ve just told one,” Dyson said． “A group 4 lie ---- small and uninteresting． Tell me a big, exciting lie．” 　　“You’ve got an ugly face, Tom Dyson．” 　　The needle fell back to zero． “No lie,” Dyson said． “So my mother was right, then． She always said I was an ugly child． But this isn’t a joke, Eva． The police use machines like this． Suppose a man kills somebody but says, “No ! No! I didn’t kill anybody．” Now that’s an excellent lie． It would send the needle round to 20． Think of a fat lie, like that----” 　　“I hate you, Tom Dyson!” Eva cried ． “Oh, how I HATE you! Is that lie big enough?” 　　Dyson was staring at the needle． “Funny,” he said． “ It seems to be stuck at 20． There must be something wrong with it． “He picked up the machine and shook it． The needle stayed at 20． “No good,” he said． “It’s never been wrong before． Eva, have you —? “He stared at HER then． He didn’t understand the look on her face ． 1．Tom had a little machine that could A．report the number of lies one told． B．show lies to be interesting or dull． C．separate jokes from lies． D．put lies into 20 groups． 2．The number 0 in the machine shows that somebody has told A．the truth． B．a small lie． C．a good lie． D．an excellent lie． 3．Was Tom ugly? A．The machine showed that he was． B．The machine showed that he wasn’t． C．Yes, because the needle didn’t move． D．No, because Eva was only joking． 4．A fat lie in the text means A．a lie that is told to the police． B．a remark that sends the needle to 20． C．a remark that makes one feel excited． D．a lie that makes one feel puzzled． 5．When the needle stayed at 20, Tom thought that A．the machine must be telling a lie． B．the machine must have made a mistake． C．Eva must be in love with him． D．Eva must be making fun of him．