【简答题】For this part, you are supposed to write a Lost Announcement in English in 100-120 words based on the following situation. Remember to write it clearly. 你(Li Yuan)丢失了一本书。写一篇失物启事。启事内容如下: (1)书名; (2)丢书的地...
【简答题】设计如图所示一水渠,它的横截面曲线是抛物线形, 宽2 m ,渠 深为1.5 m ,水面 EF 距 AB 为0.5 m . (1)求截面图中水面宽度; (2)由于情况有变,现要将此水渠改造为横截面是等腰梯形,要求渠深不变,不准往回填土,只准挖土,试求截面梯形的下边长为多大时,才能使所挖的土最少?