题目

如图，Rt△ABC中∠C=90°，∠BAC=30°，AB=8，以2为边长的正方形DEFG的一边GD在直线AB上，且点D与点A重合，现将正方形DEFG沿A﹣B的方向以每秒1个单位的速度匀速运动，当点D与点B重合时停止，则在这个运动过程中，正方形DEFG与△ABC的重合部分的面积S与运动时间t之间的函数关系图象大致是（ ）A. B. C. D. 答案：【答案】A【解析】解：如图1，CH是AB边上的高，与AB相交于点H，，∵∠C=90°，∠BAC=30°，AB=8，∴AC=AB×cos30°=8×=，BC=AB×sin30°=8×=4，∴CH=AC×BC÷AB=×4÷8=，AH= ÷AB=；（1）当0≤t≤时，S==；（2）当时，S==；（3）当6＜t≤8时，S==；综上，可得：S=，∴正方形DEFG与△ABC的重合部分的面积S与运动时间t之间的函数关第二部分：阅读理解（共25小题。第一节每小题2分，第二节每小题1分；满分45分）第一节 阅读下列短文，从每题所给的四个选项（A、B、C、D）中，选出最佳选项，并在答题卡上将该项涂黑。A gadget which makes water out of air could become the greatest household invention since the microwave.Using the same technology as a dehumidifier（除湿器），the Water Mill is able to create a ready supply of drinking water because it can always get it from an unlimited source—the air．The company behind the machine says not only does it offer an alternative to bottled water indeveloped countries, but it is a solution for the millions who face a daily water shortage．The machine works by drawing in wet air through a filter（过滤器）and over a cooling instrument which changes it into water droplets．It can produce up to 1 2 liters a day．The Water Mill will also produce more water when storms pass over, as the amount of water which is contained in the air increases．In keeping with its eco-development, the machine uses the same amount of electricity as three lights.Inventor Jonathan Ritchey said: “The demand for water is off the chart．So people are looking for freedom from water distribution systems that are shaky and unreliable.”The machine, which is about 3 feet wide, is likely to cost ￡800 when it goes on sale here in the spring．Its maker, Canadian Firm Element Four, roughly calculates that a liter of water cost around 20p to produce.Environmentalists state that half the world’s population will face water shortage because of climate change by 2080．One in five is said to lack access to safe drinking.The Water Mill is not effective in areas where the amount of water contained in the air is below about 30 percent, but in Britain that won’t be much of a problem.41．What does the underlined word “it” refer do? A．Drinking water.              B．Invention.        C．Microwave.             D．Water Mill.42．What do we learn about the machine? A．It works in the same way as microwaves． B．It is very expensive for families to afford. C．It absorbs steam and turns it into water．      D．It helps to make the water clean to drink.43．What does the passage lead us to believe? A．The cost of water will go up.  B．Bottled water will disappear sooner. C．The machine is energy saving. D．The machine will be popular worldwide.44．What’s the best title for the passage? A．A New Way to Solve Water Problem.    B．A Machine to Make Water out of Air. C．A Dehumidifier to Produce Water.     D．An Absolutely New Invention