2022第28期英语周报答案

所以BC=√14“……………………………12分18.(12分)(1)证明:如图,连接PB1交CE于点D,连接DF,EP,CB1为EP分别是BG和(的中点EP2·中甲分非…………2分又BF=2,A,B=3,故FB1=2,故FD∥AP………3分又FDC平面EFC,所以A1P∥平面EFC(2)解:由题意知AB,BC,BB1两两垂直,以B为坐标原点,以BB1的方向为轴正方向,分别以BA.BC为x轴和y轴的正方向,建立如图所示空间直角坐标系Bxyz.………………5分B则C(0,2,0),B1(0,0,3),F(2,0,3),E(0,1,3),P(0,2,).…………………6分设n=(x,y,x1)为平面EFC的法向量,则{n·EF2rEC0.可数n=(3,1)38分殳m=(x(y2,=2)为平面PFC的法向量,2x2-2y2 m·PC=0可取m=(1,1,0).………10分所以cos(n,m)3)2 9 1×1 1由题意知二面角PCFE为锐角,所以二面角PCFE的余弦值为2………12分

Li Hua第二节There was a phone number on the flyer. My dadcalled it and someone answered it was a lady. My dadasked whether she was the one who put out the flyers. Shesaid "Yes! with excitement and told us Coby, who wasvery dear to her, had been gone days before. Then we toldher that we had her puppy and we would take him to her.She told us her address at once: then we went to itWe found the lady's house, and then we knocked on ihe door. A lady opened the door, and when she saw thepuppy, she screamed with joy. We handed her the puppyfeeling proud. She wanted to give us a reward for takingcare of her puppy for her, but we said it was OK becausewe were really happy to help. So we went home tired butcontent, telling my mom the whole thing My familybecame friends with the lady, and we were all happy.

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