题目

听下面一段较长对话，回答以下小题。【1】Which gate will the man leave from?A.Gate 10. B.Gate 18. C.Gate 20【2】When will the plane take off?A.At l: 00 pm. B.At l: 30 pm. C.At 2: 00 pm. 答案：【答案】【1】B【2】C【解析】【原文】M：It’s 1：30 pm now. I’ve missed my plane. W：Well，actually，the flight has been delayed due to the bad weather. M：Great. That’s good news for me.W：May I check your luggage and see your ticket，please?M：Here you are. Do I leave from Gate 15 or Gate 10？I can’t remember.W：Gate 20.Oh，sorry，it has been changed to Gate 18如图所示，有一等腰三角形薄铁板，其底板BC=4dm，AB=xdm，现将其按图示截取一个半圆（半圆圆心在底边上，且与两腰相切），半圆的面积为y，求函数y=f（x）的解析式及定义域．