2022-2023学生双语报辅导测评官网答案，目前学生双语报答案网已经整理了2022-2023学生双语报辅导测评官网答案的各科答案和试卷，更多学生双语报答案请关注本网站。
第二节书面表达（共25分）One possible version:Dear Tom,How is it going recently?I'm sorry to know that you're having trouble in making friends.Here aresome tips for you.To begin with,be friendly to others and get on with them frankly if you want to make friends.In ad-dition,you should share happiness and sorrow with them.A saying goes that a friend in need is a friendindeed.When misunderstanding occurs,you should apologise to your friend as long as it is your fault.Lastly,wouldn't it be a good idea if you put yourself in others'shoes?As is known to all,friendshipcalls for time and effort.I hope you will find these ideas useful.Yours sincerely,Li Hua
18.【解析】审题指导(1)证PA⊥平PA⊥PB勾股定理相关线段长度面PBCPA⊥PCPO=.AE=AD△ABC是6正三角形2)建系→相关点的坐标及向量二面角B-PC-E向量数量平面PCE,平面的余弦值积公式PCB的一个法向量解：(1设D0-a,由P0-0,可得P0=.√6√6连接DE,由AE=AD可知△ADE为等边三角形，则0.1分23即△ABC外接圆半径为'了a,又△ABC为正三角形，√2由正弦定理得AB=a,PA=PB=PC=2因此PA2+PB2=AB2,从而PA⊥PB.…3分又PA2+PC2=AC2,故PA⊥PC.又PB∩PC=P,所以PA⊥平面PBC.……6分(2)由(1)得，D0⊥平面ABC,平面ABCC底面⊙O,则D0⊥底面⊙0，又AE,BCC底面⊙O,则DO⊥AE,D0⊥BC,又△ABC为正三角形，则OE⊥BC,故D0,AE,BC互相垂直，以0为坐标原点，过点0且平行于BC的直线为x轴，O龙的方向为y轴正方向，1O正1为单位长，0D所在直线为z轴，[点拨]建立直角坐标系时，若题干未给出线段长度，则可以给定线段长度便于后面计算建立如图所示的空间直角坐标系O-xyz.…7分由(1)可得E(0,1,0),A(0,-1,0),-530,P0.0.C(-2’2所以心=(-，0)，时》.8分(0,-1,设m=（x,y,z)是平面PCE的第18题解图法向量，2m·E=0-y+=0则即m·E元=01则=百2，2y=0则m=(-1,2.10分由(1)知市-(0,1，号)是平面PCB的一个法向量，记n=A2,则cos(n,m〉=n·m2w5nl·lm15[点拨]由图判断出二面角B-PC-E为锐二面角，则其余弦值为正值…11分所以二面角B-PC-E的余弦值为25…12分
