2023英语周报高三答案第3期

2023英语周报高三答案第3期已经整理完毕，供同学们学习参考，更多英语周报答案，请关注本网站。

18.解:(1)证明:连接OP,因为P为圆锥顶点,O为底面圆心所以OP⊥CD4分因为OP⊥CD,AB⊥CD,OP∩AB=O,OP,ABC平面ABE,所以CD⊥平面ABE,因为CDC平面CDE,所以平面CDE⊥平面ABE6分(2)因为圆锥PO的底面圆的周长为4x,所以AO=BO=CO=2,因为圆锥PO的母线与底面所成角的正切值为2,所以PO=4,5以O为坐标原点,OD,OB,OP所在直线分别为x轴,y轴、z轴,建立如图所示的空间直角坐标系所以A(0,-2,0),C(-2,0,0),D(2,0,0),E(0,1,2),所以CE=(2,1,2),CD=(4,0,0),AC=(-2,2,0),8分设平面CDE的一个法向量为n=(x,y,z),则2x+y+2z=0取z=1,x=0,y=-2,则n=(0,-2,1)…9分设平面ACE的一个法向量为m=(a,b,c),则=-2a+2b=0m. CE=2a+6+2c=0220取a=1,b=1,c=所以m=(1,110分设二面角A-CE-D为,易知0<22,1)·(1,1所以cos=12分所以二面角A-CE-D的余弦值为85

第一节One possible versionThe other day, a 60-year-old blind man got lost when he waswalking on the road not far from his home. It's said that he hasmental disabilitiesAfter his son sent a message in his circle of friends, themessage got around quickly. Soon people in the city set out tosearch for him. The blind man was found after three days with thehelp of so many people and his son was very grateful for what thepeople did.i hope people can keep on giving a hand to those in need

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