题目

在Rt△ABC中，∠C＝90°，c＝8，∠B＝60°，解这个三角形． 答案：【答案】a＝4，b＝4，∠A＝30°【解析】试题由已知条件易得：∠B=45°，再利用sinA=，cosA=可求得的值.试题解析：∵∠C＝90°，∠A＝45°，∴∠B＝45°，在Rt△ABC中，sinA＝，cosA＝，∴sin45°＝，cos45°＝，∴ a＝b＝8.My name is Alice. I am a school girl. My brother and I are twins(双胞胎). We both study at No.1 Middle School. We are in Class Five，Grade One. There are twenty-five boys and eighteen girls in our class.We go to school from Monday to Friday. We have no classes on Saturdays and Sundays. On school days, we usually get up at six, and have breakfast at 6:30. We come to school at 7:00. Classes begin at eight. We have four lessons in the morning and two in the afternoon. We learn Chinese, math, English, geography, history and other subjects. We like Chinese. We like English, too. Both of us are good at it. We have lunch at 12:15. At three fifty we have sports. We go home at 5:00. We have dinner at 6:00. We do homework at seven every evening and go to bed at half past nine, but sometimes we go to sleep at about ten.【1】Alice’s brother is ________ and Alice is _________A. a worker; a studentB. a student, a workerC. a student, a student【2】They have _________ at fifteen past twelve.A. breakfast B. lunch C. dinner【3】They do homework from_______ to______ every morning.A. Monday, FridayB. seven, half past nineC. six, half past eight【4】 There are_______ boys and ______ girls in their class.A. 25, 20 B. some, any C. 25, 18【5】Do they often have sports in the morning or in the afternoon?A. Yes, they doB. No, they don’tC. In the afternoon