2022英语周报 八年级外研 39答案

Dear JackHow are you doing recently I miss you very muchNow I m so excited that I can't wait to share with you anunforgettable experienceLast Friday, our school held a book sale,aimed toraise same money to help those in need. During the courseof the-after- class activity, we gathered on the playground to2e books, which were collected ahead of time. Luckily, agreat many students took an active part in this program andwe got a large amount of money.I believe our generous help is sure to have a goodeffect on children in need, especially those in themountainous areas or poverty-stricken districts. Throughour efforts, we can not only share what we have with thembut also make their life more colorful. We show our lovewhich makes our world go roundBest wishes to you!oursi hua

22.【解题思路】(1)消去参数,求得曲线C的直角坐标方程,再根据坐标的变换公式,即可求解曲线C1的方程,进而得到其极坐标方程;(2)将0=B(p>0)代入p2cos30 4gsin20=16,根据极坐标中极径的几何意义,即可求解.【解析】(1)由曲线C的参数方程为y=1 P②,为参数)①2 4X②2,得x2 4y2=16.得 2=1,所以曲线C的直角坐标方程为 x3分由x2 4y2=16,得曲线C的极坐标方程为p2cos20 4psin20=16.……9分(2)将0=B(p>0)代入p2cos20 4p2sin20=16y1- cos 2 sin gcosB⊥sin2B7分同理OBP16所以oh o= 1=110分【命题意图】本题主要考查了参数方程与普通方程的互化,极坐标方程与直角坐标方程的互化,以及极坐标的应用,着重考查了推理与运算能力,属于基础题【解后反思】1.将极坐标方程与参数方程、普通方程交织在一起,考查极坐标方程与参数方程的综合应用.将各类方程相互转化是求解该类问题的前提.解决问题时要注意:解题时,易将直线与圆的极坐标方程混淆.要熟练掌握特殊直线、圆的极坐标方程的形式2.根据极坐标中极径的几何意义解题,便于和三角知识结合起来,应用更方便

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