题目

设函数f（x）=Asin（ωx+φ）（A，ω，φ是常数，A＞0，ω＞0），若f（x）在区间上具有单调性，且，则f（x）的最小正周期为(     ) A． B． C．π   D．2π 答案：C【考点】正弦函数的图象． 【专题】三角函数的图像与性质． 【分析】由题意可得则•≥﹣，且函数的图象关于直线x= 对称，且一个对称点为（，0），由此求得ω的值，可得函数的最小正周期． 【解答】解：函数f（x）=Asin（ωx+φ）在区间上具有单调性，且， 则•≥﹣，且函数的图象关于直线x== 对 阅读理解：阅读短文，然后根据内容回答问题。 　　Scientists are trying to turn deserts(沙漠)into good land again．They want to bring water to the deserts, so people can live and grow food there．However, more and more land is becoming desert．Why? Scientists think that people are doing bad things to turn good land into desert． 　　Some places on the earth do not get very much rain, but they still do not become desert．This is because green plants are growing there．Small green plants and grass are very important to dry places．Plants do not let the hot sun make the earth even drier．Plants do not let the wind blow the soil away．When rain falls, plants hold the water．Without plants, land can become desert much more easily． 1．Do you think scientists can turn deserts into good land? ______________________________________ 2．How can they turn deserts into good land? ______________________________________ 3．Why is more and more land becoming desert? ______________________________________ 4．Why are small green plants and grass important to dry places? ______________________________________ 5．Can plants stop the wind from blowing the soil away? ______________________________________