题目

正三角形的一个顶点位于坐标原点,另外两个顶点在抛物线y2=72x上,则这个正三角形的边长是    . 答案：解析:设正△OAB的顶点A、B在抛物线上,A(x1,y1)、B(x2,y2),则y12=72x1,y22=72x2.由|OA|=|OB|,得x12+y12=x22+y22.∴x12+72x1-x22-72x2=0.∴x1=x2.∴线段AB关于x轴对称.∴∠AOx=30°.∴=tan30°=.∵x1=,∴y1=72.∴|AB|=144.答案:144阅读下面的短文，然后按照要求写一篇150词左右的英语短文。【阅读材料】The worst winter snow storm of 5 decades years turned South China into a world of white colour. Chinese Spring Festival approaching, the snow storm lasted for dozens of days and made it a hard way home for hundreds of thousands of people working outside their hometown.To those who were eager to go back home to reunion with their families after one or more years of departure(分别), the snow storm added to their anxiety and disappointment. The unwelcoming snow storm totally disturbed the step of the city, of the country. However, any nature disaster is not allowed to destroy our life as long as there is love. In the departure hall of railway station, the railway staff made explanation to the waiting passengers patiently , providing them with hot water and food. Doctors and nurses volunteered to help the sick. Traffic police and volunteers from the communities cleared the roads on every cold morning. Kind people from every corner of the country donated their money or clothes to help those waiting at the railway stations go through the hard time. True love exists in the world.【写作内容】1．概括短文的内容要点，该部分的字数大约30词左右；2．以大约120词写一篇记叙文，描写你或你身边的人帮助他人的一次经历，并包括如下要点：       (1)叙述你或身边的人帮助他人的一次真实或虚构的经历。        (2)你或身边的人是怎么看待这次经历的？       (3)作为中学生，你觉得还可以通过什么方式去帮助有需要的人？