英语周报答案2022-2022七年级上册35期

(1-cos C)+2-1-2cos C,.. 2sin Asin B-1.X A=B,, sinA=2,A-4,B=4,C-2则△ABC为等腰直角三角形.故选A5.A【解析】将已知等式2 acos e=c,利用正弦定理化简得2 sin acos B=sinC,∵sinC=sin(A+B)=sin Acos b+cos Asin B,, 2sin Acos B= sin Acos Bcos Asin B,即 sin Acos e- cos Asin B=sin(A一B)=0,A与B都为△ABC的内角,∴A-B=0,即A=B,由第二个等式变形得 sin Asin b(2-cosC)=

第二节One possible versionDear mr. smithIm writing to ask for a three-day leave, for I can'Iattend your English classes from Monday to Wednesday nexOwing to a severe headache, I have made an appoint-ment with a specialist. and my mother will take me to seehim. It's a great pity that I will miss your interesting lessons but I hope you will excuse my absence. I promise tomake up for the missed lessons after I return to school.Your kind permission will be greatly appreciatedYeLi Hua

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