2022英语周报初一广东答案

22.(1)由直线l的参数方程为参数),消去t得x-y=1,所以直线的极坐标方程为pcos0…2分由p-2acoso(a>0).+ p'-2apcosd(a>0)由x=pcos0,y=psin0代入,得曲线C的直角坐标方程为x2+y2=2ax(a>0).……5分(2)显然M在直线l上,将直线l的参数方程与C的直角坐标方程联立,得2-√2(1+a)t+1=0.则△=[√2(1+a)]2-4>0且t1+2=√2(1+a),tt2=1………7分设点P,Q分别对应参数t1,2恰为上述方程的根则|MP|=4,|MQ|=42,|RQ|=|1-12|由题设得|1-t2|2=4t12则有(t1+t2)2=81t2,得a=1或a=-3因为a>0,且a=1满足△>0.所以a10分

书面表达One possible version:NOTICEA sports meeting will be held in the playground of our school from next Thursday to FridayAs you know, the pressure of study is very heavy now, especially for those senior 3. So the purpose of the sports meeting is to letevery student get relaxed, as a result of which we students can live happily and heal thilyEveryone is welcome to take part in it. Those who perform excellently at the sports meeting will get prizes. But don' t take theresults so serously because taking part is more important than the result. Good luck to everyone!

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