2023九师联盟生物卷及答案

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16.9√39【解析】由题可知在过E的所有平面截球所得截面中，最大截面为大圆，设球O的半径为R,则πR2=16π，解得R=4,最小的截面为以BC为直径的小圆，则π(C)'=9x,解得BC=6,设△BCD的中心为O1,连接AO,则球心O在线段AO1上，连接OB,0,B,则0B=R=4,0B=号×号BC=2√3，所以OO=√/OB2-OB2=2,所以AO1=6,连接AE,则AE=√AO十OE=√39，所以正三棱锥A-BCD的侧面积为3X号X6X√39=9√39

第四部分：写作第一节Dear Jack,In order to make students'life colorful,our school has decided to hold a calligraphy and painting show inthe lecture hall.I'm writing to invite you to take part in the activity.You are always interested in painting,so I consider it a good opportunity for you to present your works.All works,whose themes are positive and about school life,are welcome.I am sure you will be happy to hearabout the news.Please hand in your painting before October 31st.Looking forward to seeing your wonderful work on the show.Yours,Li Hua