2022年三角形四心的向量性质及应用20120516 .pdf
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1、-1-三角形“四心”的向量性质及其应用三角形“四心”的概念介绍(1)重心三条中线的交点:重心将中线长度分成2:1;(2)外心三边中垂线的交点(外接圆的圆心):外心到三角形各顶点的距离相等;(3)垂心三条高线的交点:高线与对应边垂直;(4)内心三条内角平分线的交点(内切圆的圆心):角平分线上的任意点到角两边的距离相等工具:O为ABC内一点,则有:0OCSOBSOASOABOCAOBC证明:延长AO交BC于D,如图必有:|OAODSSSOABOCAOBC,|BCBDSSSOABOCAOAB,|BCCDSSSOABOCAOCA;-(*)由DOA,共线,得:0|ODODOAOA进而得:0|ODOAOA
2、OD -由CDB,共线,得:OCBCBDOBBCCDOD|-由得:OAOAOD|0|OCBCBDOBBCCD代入(*)结论得OASSSOABOCAOBCOBSSSOABOCAOCA0OCSSSOABOCAOAB消去分母得:0OCSOBSOASOABOCAOBC证毕.另证:作ACOGABOH/,/,如图:AGOH为平行四边形;由OCSOBSOASOABOCAOBC)()(ACOASABOASOASOABOCAOBCACSABSOASOABOCAABC)(ACSSABSSOASABCOABABCOCAABC)(ACACAHABABAGOASABC)(AHAGOASABC0)(AOOASABCABC
3、ODABCODHFEG-2-反方向思考:设O在ABC的内部,若有正实数321,满足:0321OCOBOA,必有:AOBCOABOCSSS:321证明:作:OAOA1,OBOB2,OCOC3则OAOB0OC,则O为CBA的重心,则:OBAOACOCBSSS.设为S又SSSSSSSSSAOBOBACOAOACBOCOCB2!1332从而得:AOBCOABOCSSSSSS:211332321验证式思考:先证引理:若ba,不共线,对p,有0pa且0pb,必有.0p证明:若.0p必有pa且pb,得ba/,与题设矛盾,故必有.0p再证:设BOC,COA,则2AOB;由)(OCSOBSOASOAOABOCA
4、OBCOCOASOBOASOASOABOCAOBC2cos)2sin(21)2cos(sin21sin212OCOAOBOAOBOAOAOCOAOCOBcos)sin()cos(sinsin212OCOBOA)(sinsin212OCOBOA0)sin(sin212OCOBOA;有对称性知:0)(OCSOBSOASOBOABOCAOBC,又OA,OB不共线,故:必有0OCSOBSOASOABOCAOBC成立一、三角形的重心的向量表示及应用知识:G 是ABC的重心)(31ACABAG0GCGBGA)(31OCOBOAOG (O为该平面上任意一点)略证:1:1:1:GABGCAGBCSSS,得:0
5、GCGBGA变式:已知 DEF,分别为ABC的边 BCACAB,的中点则0CFBEAD二、三角形的外心的向量表示及应用知识:O是ABC的外心222|OCOBOAOCOBOAABCOABCABCO文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编
6、码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q
7、8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编
8、码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q
9、8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编
10、码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q
11、8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8-3-02sin2sin2sinOCCOBBOAA略证:CBASSSOABOCAOBC2sin:2sin:2sin:,得:02sin2sin2sinOCCOBBOAA
12、常用结论:O是ABC的外心.2|;2|22ACAOACABAOAB三、三角形的垂心的向量表示及应用知识:H是ABC的垂心HAHCHCHBHBHA222222|ABHCCAHBBCHA0tantantanHCCHBBHAA略证:CBASSSHABHCAHBCtan:tan:tan:,得:0tantantanHCCHBBHAA扩展:若O是ABC的外心,点H满足:OCOBOAOH,则H是ABC的垂心证明:如图:BE为直径,H为垂心,O为外心,D为BC中点;有:为平行四边形AHCEEACHABEAABCHECAHBCECBCAH/进而得到:,/ECAH且ECAH,即:ECAH;又易知:OCOBODEC
13、2;故:OAOHOCOBAH,即:OCOBOAOH又:OGOCOBOA3(G为重心),故:OGOH3;故:得到欧拉线:ABC的外心O,重心G,垂心H三点共线(欧拉线),且GHOG21证毕四、三角形的内心的向量表示及应用知识:I是ABC的内心0|0|0|CBCBCACACIBCBCBABABIACACABABAI0|0|0|CACABCBCCIBABACBCBBIACACBABAAI0ICcIBbIAacbaOCcOBbOAaOI0sinsinsinICCIBBIAA注:式子中|,|,|ABcCAbBCa,O为任一点ABDOHCE文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H
14、8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H
15、5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H
16、8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H
17、5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H
18、8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H
19、5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H
20、8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8-4-略证:CBAcbaSSSIABICAIBCsin:sin:sin:,得之五欧拉线:ABC的外心O,重心G,垂心H三点共线(欧拉线),且GHOG21(前已证)测试题一选择题1O是ABC所在平面上一定点,动点P满足)(ACABOAOP,,0,则点P的轨迹一定通过ABC的()A外心B内心C重心D垂心2(03 全国理 4)O是ABC所在平面上一定点,动点P满足)(ACACABABOAOP,,0,则点P的轨迹一定通过ABC的(
21、)A外心B内心C重心D垂心3O是ABC所在平面上一定点,动点P满足)coscos(CACACBABABOAOP,R,则点P的轨迹一定通过ABC的()A外心B内心C重心D垂心4O是ABC所在平面上一定点,动点P满足)sinsin(CACACBABABOAOP,,0,则点P的轨迹一定通过ABC的()A外心B内心C重心D垂心5O是ABC所在平面上一定点,动点P满足2coscosOBOCABACOPABBACC,R,则点P的轨迹一定通过ABC的()A外心B内心C重心D垂心6O是ABC所在平面上一定点,动点P满足)21()1()1(31OCOBOAOP,*R,则点P的轨迹一定通过ABC的()A内心B垂心
22、C重心DAB 边的中点7已知O是ABC的重心,动点P满足)22121(31OCOBOAOP,则点P一定为ABC的()AAB 边中线的中点BAB 边中线的三等分点(非重心)C重心DAB 边的中点8在ABC中,动点P满足:CPABCBCA222,则P点轨迹一定通过ABC的()外心内心C重心D垂心9已知ABC三个顶点CBA、及平面内一点P,满足0PCPBPA,若实数满足:APACAB,则的值为()A2 B23C3 D6 10设点P是ABC内一点,用ABCS表示ABC的面积,令ABCPBCSS1,ABCPCASS2,ABCPABSS3文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8
23、V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5
24、V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8
25、V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5V1 HS5C7Q8Q6D3 ZR9H8V8C9M8文档编码:CY2Y4H6H5
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