人教版七年级上册英语周报答案

11解:(1)∵Cb=2BA,|Cb∴BA∥CD,|AB|=1.∵BA·BC=1,∴|BA|· I BCIcos∠ABC=1,即1×2cos∠ABC=1,c∠ABC=1(8分)∵∠ABC∈(0,r),∠ABC=3(10分)(2)设BO=tBC(0≤r≤1)则C=(1-)BC,∴OA=BA-BO=BA-tBCC CD=2 BA (1-t苏·=(B-B)·[b (1-n)B=2BA2 (1-3)BA.BC-(1-1)B2BA2 (1-3t)BA(1-t BC=2×12 (1-3n×1-t(1-0)×4=4r2-7t 3.(18分)当=8时,即B0=7OC时,OA·OD最小(20分)

书面表达【参考范文】My Favourite BookOf all the books I have read. I love A Dream of theRed Mansions mostIt is my favorite not because it was written by CaoXueqin, a famous novelist in Qing Dynasty. Rather, Ideeply value the book and have read it over 10 times, first-ly, for the moving love story between Jia Baoyu and LinDaiyu. Besides, if given enough patience and devotion, thenovel will also reveal the rise and decline of a famous royalfamily to its readers. What I also enjoy about the book isits language and writing style of Cao Xueqin, which had aprofound effect on the writers of his times and later gener-ationsAll in all, A Dream of the Red Mansions has won myheart and I am convinced that it deserves yours too

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