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專題04巧用中點(diǎn)解決幾何問題一、【知識(shí)回顧】方法與技巧:中點(diǎn)問題常見輔助線做法①遇到三角形邊上的中點(diǎn),考慮構(gòu)造三角形的中位線②遇到直角三角形斜邊的中點(diǎn),考慮直角三角形斜邊的中線性質(zhì)③遇到等腰三角形底邊的中點(diǎn),考慮等腰三角形“三線合一”的性質(zhì)④遇到中點(diǎn)+垂線,角平分線+垂線,考慮垂直平分線的性質(zhì)⑤遇到面積類型題,考慮三角形中線平分面積⑥遇到線段數(shù)量關(guān)系,考慮倍長中線構(gòu)造全等三角形二、【考點(diǎn)類型】考點(diǎn)1:構(gòu)造三角形的中位線典例1:(2022秋·四川眉山·九年級(jí)??计谥校┤鐖D,SKIPIF1<0中,SKIPIF1<0,點(diǎn)E是SKIPIF1<0的中點(diǎn),若SKIPIF1<0平分SKIPIF1<0,SKIPIF1<0,線段SKIPIF1<0的長為(

)A.1cm B.2cm C.3cm D.4cm【變式1】(2022秋·山東濟(jì)寧·九年級(jí)濟(jì)寧市第十五中學(xué)統(tǒng)考期末)如圖,在SKIPIF1<0中,SKIPIF1<0平分SKIPIF1<0,SKIPIF1<0于點(diǎn)E,點(diǎn)F是SKIPIF1<0的中點(diǎn),若SKIPIF1<0,SKIPIF1<0,則SKIPIF1<0的長為(

).A.2 B.3 C.4 D.5【變式2】(2022春·全國·八年級(jí)假期作業(yè))已知:如圖,在SKIPIF1<0中,中線SKIPIF1<0交于點(diǎn)SKIPIF1<0分別是SKIPIF1<0的中點(diǎn).求證:(1)SKIPIF1<0;(2)SKIPIF1<0和SKIPIF1<0互相平分.【變式3】(2021·全國·九年級(jí)專題練習(xí))如圖,在Rt△ABC中,∠ACB=90°,點(diǎn)D,E分別是邊AB,AC的中點(diǎn),延長BC到點(diǎn)F,使CF=SKIPIF1<0BC.連結(jié)CD、EF,那么CD與EF相等嗎?請(qǐng)證明你的結(jié)論.考點(diǎn)2:直角三角形斜邊的鵝中線典例2:(2022秋·福建福州·八年級(jí)統(tǒng)考期中)如圖,在一塊含SKIPIF1<0角的三角板(SKIPIF1<0)的頂點(diǎn)SKIPIF1<0處作SKIPIF1<0,垂足為SKIPIF1<0.在SKIPIF1<0的右側(cè)作SKIPIF1<0使SKIPIF1<0,連接SKIPIF1<0,SKIPIF1<0的延長線交SKIPIF1<0于SKIPIF1<0.設(shè)SKIPIF1<0,SKIPIF1<0,則下列式子成立的是(

)A.SKIPIF1<0 B.SKIPIF1<0C.SKIPIF1<0 D.SKIPIF1<0【變式1】(2022秋·新疆烏魯木齊·九年級(jí)??计谥校┤鐖D,SKIPIF1<0SKIPIF1<0中,SKIPIF1<0,SKIPIF1<0,SKIPIF1<0,SKIPIF1<0是SKIPIF1<0內(nèi)部的一個(gè)動(dòng)點(diǎn),且滿足SKIPIF1<0,則線段SKIPIF1<0長的最小值為(

)A.2 B.1 C.SKIPIF1<0 D.SKIPIF1<0【變式2】(2022秋·廣西貴港·九年級(jí)統(tǒng)考期中)如圖,在SKIPIF1<0中,SKIPIF1<0,由圖中的尺規(guī)作圖痕跡得到的射線SKIPIF1<0與SKIPIF1<0交于點(diǎn)E,點(diǎn)F為SKIPIF1<0的中點(diǎn),連接SKIPIF1<0,若SKIPIF1<0,則SKIPIF1<0的周長為(

)A.SKIPIF1<0+1 B.SKIPIF1<0+2 C.2SKIPIF1<0+2 D.2SKIPIF1<0+3【變式3】(2021·廣東廣州·統(tǒng)考中考真題)如圖,在四邊形ABCD中,SKIPIF1<0,點(diǎn)E是AC的中點(diǎn),且SKIPIF1<0(1)尺規(guī)作圖:作SKIPIF1<0的平分線AF,交CD于點(diǎn)F,連結(jié)EF、BF(保留作圖痕跡,不寫作法);(2)在(1)所作的圖中,若SKIPIF1<0,且SKIPIF1<0,證明:SKIPIF1<0為等邊三角形.考點(diǎn)3:等腰三角形三線合一性質(zhì)典例3:(2023秋·江西南昌·八年級(jí)統(tǒng)考期末)如圖所示,SKIPIF1<0中,SKIPIF1<0,SKIPIF1<0于點(diǎn)E,SKIPIF1<0于點(diǎn)D,交SKIPIF1<0于F.(1)若SKIPIF1<0,求SKIPIF1<0的度數(shù);(2)若點(diǎn)F是SKIPIF1<0的中點(diǎn),求證:SKIPIF1<0.【變式1】(2020·內(nèi)蒙古赤峰·統(tǒng)考中考真題)如圖,SKIPIF1<0中,AB=AC,AD是∠BAC的平分線,EF是AC的垂直平分線,交AD于點(diǎn)O.若OA=3,則SKIPIF1<0外接圓的面積為(

)A.SKIPIF1<0 B.SKIPIF1<0 C.SKIPIF1<0 D.SKIPIF1<0【變式2】(2022秋·浙江杭州·八年級(jí)統(tǒng)考期末)如圖,在△ABC中,AB=AC,AD平分∠BAC,DE⊥AB于E點(diǎn),DF⊥AC于點(diǎn)F,則下列四個(gè)結(jié)論:①AD上任意一點(diǎn)到AB,AC兩邊的距離相等;②AD⊥BC且BD=CD;③∠BDE=∠CDF;④AE=AF.其中正確的有()A.②③ B.①③ C.①②④ D.①②③④【變式3】(2022秋·吉林長春·八年級(jí)??茧A段練習(xí))如圖所示,在SKIPIF1<0中,SKIPIF1<0,直線EF是AB的垂直平分線,D是BC的中點(diǎn),M是EF上一個(gè)動(dòng)點(diǎn),SKIPIF1<0的面積為12,SKIPIF1<0,則SKIPIF1<0周長的最小值是_______________.考點(diǎn)4:垂直平分線性質(zhì)典例4:(2022·新疆烏魯木齊·??家荒#┤鐖D,在矩形ABCD中,AB=4cm,對(duì)角線AC與BD相交于點(diǎn)O,DE⊥AC,垂足為E,AE=3CE,則DE的長為(

)A.SKIPIF1<0 B.2cm C.SKIPIF1<0 D.SKIPIF1<0【變式1】(2021·四川內(nèi)江·統(tǒng)考中考真題)如圖,矩形SKIPIF1<0中,SKIPIF1<0,SKIPIF1<0,對(duì)角線SKIPIF1<0的垂直平分線SKIPIF1<0交SKIPIF1<0于點(diǎn)SKIPIF1<0、交SKIPIF1<0于點(diǎn)SKIPIF1<0,則線段SKIPIF1<0的長為__.【變式2】(2020·江西·統(tǒng)考中考真題)如圖,SKIPIF1<0平分SKIPIF1<0,SKIPIF1<0,SKIPIF1<0的延長線交SKIPIF1<0于點(diǎn)SKIPIF1<0,若SKIPIF1<0,則SKIPIF1<0的度數(shù)為__________.【變式3】(2020·江蘇連云港·中考真題)如圖,在四邊形SKIPIF1<0中,SKIPIF1<0,對(duì)角線SKIPIF1<0的垂直平分線與邊SKIPIF1<0、SKIPIF1<0分別相交于SKIPIF1<0、SKIPIF1<0.(1)求證:四邊形SKIPIF1<0是菱形;(2)若SKIPIF1<0,SKIPIF1<0,求菱形SKIPIF1<0的周長.考點(diǎn)5:中線平分面積典例5:(2022秋·安徽滁州·八年級(jí)??茧A段練習(xí))如圖,SKIPIF1<0的面積為SKIPIF1<0,SKIPIF1<0垂直SKIPIF1<0的平分線SKIPIF1<0于SKIPIF1<0,則SKIPIF1<0的面積為(

)A.SKIPIF1<0 B.SKIPIF1<0 C.SKIPIF1<0 D.SKIPIF1<0【變式1】(2021秋·內(nèi)蒙古鄂爾多斯·八年級(jí)統(tǒng)考期末)如圖,在SKIPIF1<0中,SKIPIF1<0平分SKIPIF1<0,SKIPIF1<0于點(diǎn)P,已知SKIPIF1<0的面積為SKIPIF1<0,則陰影部分的面積為(

)A.SKIPIF1<0 B.SKIPIF1<0 C.SKIPIF1<0 D.SKIPIF1<0【變式2】(2021秋·福建福州·八年級(jí)福建省福州延安中學(xué)??计谥校┤鐖D,△ABC中,AC=DC=3,AD平分∠BAC,BD⊥AD于D,E為AC的中點(diǎn),則圖中兩個(gè)陰影部分面積之差的最大值為(

)A.1.5 B.3 C.4.5 D.6【變式3】(2023春·江蘇·八年級(jí)階段練習(xí))如圖,在平行四動(dòng)形紙板SKIPIF1<0中,點(diǎn)SKIPIF1<0,SKIPIF1<0,SKIPIF1<0分別為SKIPIF1<0,SKIPIF1<0,SKIPIF1<0的中點(diǎn),連接SKIPIF1<0,SKIPIF1<0,SKIPIF1<0.將一飛鏢隨機(jī)投擲到平行四邊形紙板上,則飛鏢落在陰影部分的概率為________.考點(diǎn)6:倍長中線,構(gòu)全等典例6:(2022秋·甘肅定西·八年級(jí)統(tǒng)考期中)如圖,在SKIPIF1<0中,SKIPIF1<0,SKIPIF1<0,SKIPIF1<0是SKIPIF1<0邊上的中線,則SKIPIF1<0的取值范圍是(

)A.SKIPIF1<0 B.SKIPIF1<0 C.SKIPIF1<0 D.SKIPIF1<0【變式1】(2021秋·河南信陽·八年級(jí)校考期中)如圖,已知AC平分∠DAB,CE⊥AB于E,AB=AD+2BE,則下列結(jié)論:①AB+AD=2AE;②∠DAB+∠DCB=180°;③CD=CB;④S△ACE﹣2S△BCE=S△ADC;其中正確結(jié)論的個(gè)數(shù)是()A.1個(gè) B.2個(gè) C.3個(gè) D.4個(gè)【變式2】(2022秋·浙江杭州·八年級(jí)校聯(lián)考階段練習(xí))如圖,在SKIPIF1<0中,SKIPIF1<0,D為邊AB的中點(diǎn),E、F分別為邊AC、BC上的點(diǎn),且SKIPIF1<0,SKIPIF1<0若SKIPIF1<0,SKIPIF1<0,則SKIPIF1<0______SKIPIF1<0,線段AB的長度SKIPIF1<0______.【變式3】(2022秋·山東濱州·八年級(jí)統(tǒng)考期中)如圖,四邊形ABCD中,∠BAD=120°,∠B=∠D=90°,在BC、CD上分別找一點(diǎn)M、N,使△AMN周長最小時(shí),則∠AMN+∠ANM的度數(shù)是________.鞏固訓(xùn)練一、單選題1.(2020秋·湖北黃石·八年級(jí)黃石八中校考期中)如圖,AD是△ABC的中線,E是AD上一點(diǎn),延長BE交AC于F,若BE=AC,BF=9,CF=6,則AF的長度為(

)A.1 B.1.5 C.2 D.32.(2023·全國·九年級(jí)專題練習(xí))如圖,在四邊形SKIPIF1<0中,SKIPIF1<0,SKIPIF1<0,SKIPIF1<0,SKIPIF1<0,SKIPIF1<0,點(diǎn)SKIPIF1<0是SKIPIF1<0的中點(diǎn),則SKIPIF1<0的長為(

).A.2 B.SKIPIF1<0 C.SKIPIF1<0 D.33.(2021春·浙江杭州·八年級(jí)杭州外國語學(xué)校??计谥校┤鐖D,在?ABCD中,BE垂直平分CD于點(diǎn)E,且∠BAD=45°,AD=3,則?ABCD的對(duì)角線AC的長為()A.SKIPIF1<0 B.5SKIPIF1<0 C.5SKIPIF1<0 D.2SKIPIF1<04.(2022秋·浙江寧波·八年級(jí)校聯(lián)考期中)如圖,O為數(shù)軸原點(diǎn),A,B兩點(diǎn)分別對(duì)應(yīng)SKIPIF1<0、3,作腰長為4的等腰SKIPIF1<0,連接SKIPIF1<0,以O(shè)為圓心,SKIPIF1<0長為半徑畫弧交數(shù)軸于點(diǎn)M,則點(diǎn)M對(duì)應(yīng)的實(shí)數(shù)為()A.SKIPIF1<0 B.4 C.SKIPIF1<0 D.2.55.(2023秋·廣東惠州·八年級(jí)??计谀┤鐖D,在SKIPIF1<0中,SKIPIF1<0,SKIPIF1<0于點(diǎn)SKIPIF1<0,SKIPIF1<0為SKIPIF1<0的中點(diǎn),SKIPIF1<0為SKIPIF1<0上一動(dòng)點(diǎn).若SKIPIF1<0腰上的中線長是3.則SKIPIF1<0周長的最小值為()A.4 B.5 C.6 D.76.(2022秋·江蘇無錫·八年級(jí)校聯(lián)考期中)如圖,SKIPIF1<0,SKIPIF1<0,SKIPIF1<0,SKIPIF1<0,點(diǎn)D是BC的中點(diǎn),將SKIPIF1<0沿AD翻折得到SKIPIF1<0,連結(jié)BE,則線段BE的長為()A.2 B.SKIPIF1<0 C.SKIPIF1<0 D.SKIPIF1<07.(2023秋·四川雅安·九年級(jí)??计谥校┤鐖D,在SKIPIF1<0中,點(diǎn)SKIPIF1<0分別是邊SKIPIF1<0的中點(diǎn),點(diǎn)SKIPIF1<0是線段SKIPIF1<0上的一點(diǎn),連接SKIPIF1<0,SKIPIF1<0,且SKIPIF1<0,SKIPIF1<0,則SKIPIF1<0的長是(

)A.3 B.4 C.5 D.68.(2023·河北秦皇島·統(tǒng)考一模)如圖,在SKIPIF1<0中,SKIPIF1<0,將SKIPIF1<0繞頂點(diǎn)C順時(shí)針旋轉(zhuǎn)得到SKIPIF1<0,D是SKIPIF1<0的中點(diǎn),連接BD,若SKIPIF1<0,SKIPIF1<0,則線段SKIPIF1<0的最大值為(

)A.SKIPIF1<0 B.SKIPIF1<0 C.3 D.49.(2022春·浙江杭州·九年級(jí)??茧A段練習(xí))如圖,在SKIPIF1<0中,中線SKIPIF1<0、SKIPIF1<0相交于點(diǎn)O,連接SKIPIF1<0,則SKIPIF1<0的面積與SKIPIF1<0的面積比是()A.SKIPIF1<0 B.SKIPIF1<0 C.2 D.410.(2022春·江蘇南京·八年級(jí)校考期中)如圖,四邊形SKIPIF1<0中,SKIPIF1<0與SKIPIF1<0不平行,SKIPIF1<0,SKIPIF1<0分別是SKIPIF1<0、SKIPIF1<0的中點(diǎn),SKIPIF1<0,SKIPIF1<0,則SKIPIF1<0的長可能是(

)A.4 B.6 C.8 D.1011.(2023春·江蘇·八年級(jí)專題練習(xí))如圖,在正SKIPIF1<0中,SKIPIF1<0,SKIPIF1<0,連接SKIPIF1<0,若M、N分別為線段SKIPIF1<0、SKIPIF1<0的中點(diǎn),則線段SKIPIF1<0的長度等于()A.SKIPIF1<0 B.SKIPIF1<0 C.SKIPIF1<0 D.312.(2023春·江蘇·八年級(jí)專題練習(xí))如圖,已知四邊形SKIPIF1<0中,SKIPIF1<0,點(diǎn)E、F分別是邊SKIPIF1<0的中點(diǎn),連接SKIPIF1<0,則SKIPIF1<0的長是()A.SKIPIF1<0 B.5 C.SKIPIF1<0 D.1013.(2022秋·廣東梅州·九年級(jí)??奸_學(xué)考試)如圖,射線SKIPIF1<0射線CD,SKIPIF1<0與SKIPIF1<0的平分線交于點(diǎn)E,SKIPIF1<0,點(diǎn)P是射線AB上的一動(dòng)點(diǎn),連結(jié)PE并延長交射線CD于點(diǎn)SKIPIF1<0給出下列結(jié)論:SKIPIF1<0是直角三角形;SKIPIF1<0;SKIPIF1<0設(shè)SKIPIF1<0,SKIPIF1<0,則y關(guān)于x的函數(shù)表達(dá)式是SKIPIF1<0,其中正確的是SKIPIF1<0

SKIPIF1<0A.SKIPIF1<0 B.SKIPIF1<0 C.SKIPIF1<0 D.SKIPIF1<014.(2023春·八年級(jí)課時(shí)練習(xí))如圖,在正方形SKIPIF1<0中,點(diǎn)E,G分別在SKIPIF1<0,SKIPIF1<0邊上,且SKIPIF1<0,SKIPIF1<0,連接SKIPIF1<0、SKIPIF1<0,SKIPIF1<0平分SKIPIF1<0,過點(diǎn)C作SKIPIF1<0于點(diǎn)F,連接SKIPIF1<0,若正方形的邊長為4,則SKIPIF1<0的長度是()A.SKIPIF1<0 B.SKIPIF1<0 C.SKIPIF1<0 D.SKIPIF1<015.(2023春·八年級(jí)課時(shí)練習(xí))如圖,在SKIPIF1<0ABC中,點(diǎn)E在邊AC上,EB=EA,∠A=2∠CBE,延長BD到F,使DF=DB,連接CF,過點(diǎn)C作CD⊥BF于點(diǎn)D,BD=16,AC=22,則邊BC的長為()A.8SKIPIF1<0 B.9SKIPIF1<0 C.10SKIPIF1<0 D.12SKIPIF1<0二、填空題16.(2020·天津·中考真題)如圖,SKIPIF1<0的頂點(diǎn)C在等邊SKIPIF1<0的邊SKIPIF1<0上,點(diǎn)E在SKIPIF1<0的延長線上,G為SKIPIF1<0的中點(diǎn),連接SKIPIF1<0.若SKIPIF1<0,SKIPIF1<0,則SKIPIF1<0的長為_______.17.(2021·全國·九年級(jí)專題練習(xí))如圖,在直角坐標(biāo)系中,⊙A的半徑為2,圓心坐標(biāo)為(4,0),y軸上有點(diǎn)B(0,3),點(diǎn)C是⊙A上的動(dòng)點(diǎn),點(diǎn)P是BC的中點(diǎn),則OP的范圍是_____.18.(2022春·九年級(jí)課時(shí)練習(xí))如圖,在半徑為3的⊙O中,AB是直徑,AC是弦,D是SKIPIF1<0的中點(diǎn),AC與BD交于點(diǎn)E.若E是BD的中點(diǎn),則AC的長是_______.19.(2022·天津·統(tǒng)考中考真題)如圖,已知菱形SKIPIF1<0的邊長為2,SKIPIF1<0,E為SKIPIF1<0的中點(diǎn),F(xiàn)為SKIPIF1<0的中點(diǎn),SKIPIF1<0與SKIPIF1<0相交于點(diǎn)G,則SKIPIF1<0的長等于___________.20.(2021·甘肅武威·統(tǒng)考中考真題)如圖,在矩形SKIPIF1<0中,SKIPIF1<0是SKIPIF1<0邊上一點(diǎn),SKIPIF1<0是SKIPIF1<0邊的中點(diǎn),SKIPIF1<0,則SKIPIF1<0________SKIPIF1<0.21.(2021·四川內(nèi)江·統(tǒng)考中考真題)如圖,矩形SKIPIF1<0,SKIPIF1<0,SKIPIF1<0,點(diǎn)SKIPIF1<0在SKIPIF1<0軸正半軸上,點(diǎn)SKIPIF1<0在SKIPIF1<0軸正半軸上.當(dāng)點(diǎn)SKIPIF1<0在SKIPIF1<0軸上運(yùn)動(dòng)時(shí),點(diǎn)SKIPIF1<0也隨之在SKIPIF1<0軸上運(yùn)動(dòng),在這個(gè)運(yùn)動(dòng)過程中,點(diǎn)SKIPIF1<0到原點(diǎn)SKIPIF1<0的最大距離為__.22.(2022秋·九年級(jí)單元測試)如圖,SKIPIF1<0的半徑為2,圓心SKIPIF1<0的坐標(biāo)為SKIPIF1<0,點(diǎn)SKIPIF1<0是SKIPIF1<0上的任意一點(diǎn),SKIPIF1<0,且SKIPIF1<0、SKIPIF1<0與SKIPIF1<0軸分別交于SKIPIF1<0、SKIPIF1<0兩點(diǎn),若點(diǎn)SKIPIF1<0、點(diǎn)SKIPIF1<0關(guān)于原點(diǎn)對(duì)稱,當(dāng)線段SKIPIF1<0最短時(shí),點(diǎn)SKIPIF1<0的坐標(biāo)為______.24.(2023秋·江西宜春·八年級(jí)??计谀┤鐖D,在Rt△ABC中,∠BAC=90°,AB=3,AC=4,P為邊BC上一動(dòng)點(diǎn),PE⊥AB于E,PF⊥AC于F,M為EF的中點(diǎn),則AM的最小值是______________.26.(2022·安徽·統(tǒng)考中考真題)如圖,平行四邊形OABC的頂點(diǎn)O是坐標(biāo)原點(diǎn),A在x軸的正半軸上,B,C在第一象限,反比例函數(shù)SKIPIF1<0的圖象經(jīng)過點(diǎn)C,SKIPIF1<0的圖象經(jīng)過點(diǎn)B.若SKIPIF1<0,則SKIPIF1<0________.27.(2021·廣東深圳·統(tǒng)考中考真題)如圖,已知SKIPIF1<0,SKIPIF1<0是角平分線且SKIPIF1<0,作SKIPIF1<0的垂直平分線交SKIPIF1<0于點(diǎn)F,作SKIPIF1<0,則SKIPIF1<0周長為________.28.(2022·江蘇無錫·統(tǒng)考中考真題)如圖,正方形ABCD的邊長為8,點(diǎn)E是CD的中點(diǎn),HG垂直平分AE且分別交AE、BC于點(diǎn)H、G,則BG=________.29.(2022秋·八年級(jí)課時(shí)練習(xí))如圖,△ABC的面積是12,點(diǎn)D,E,F(xiàn),G分別為BC,AD,BE,CE的中點(diǎn),則△AFG的面積是_____.30.(2022春·江蘇無錫·七年級(jí)宜興市實(shí)驗(yàn)中學(xué)??茧A段練習(xí))如圖,在SKIPIF1<0中,點(diǎn)D在BC上,點(diǎn)E是AD的中點(diǎn),點(diǎn)F在BE上,且SKIPIF1<0,若SKIPIF1<0,則SKIPIF1<0________.三、解答題31.(2023·安徽合肥·合肥一六八中學(xué)??家荒#┤鐖D,在△ABC中,∠ACB=90°,BC>AC,CD⊥AB于點(diǎn)D,點(diǎn)E是AB的中點(diǎn),連接CE.(1)若AC=3,BC=4,求CD的長;(2)求證:BC2﹣AC2=2DE?AB;(3)求證:CE=SKIPIF1<0AB.32.(2021春·廣西南寧·八年級(jí)南寧市第四十七中學(xué)??计谥校┮阎喝鐖D,在SKIPIF1<0中,SKIPIF1<0,SKIPIF1<0為SKIPIF1<0的中點(diǎn),SKIPIF1<0、SKIPIF1<0分別在SKIPIF1<0、SKIPIF1<0上,且SKIPIF1<0于SKIPIF1<0.求證:SKIPIF1<0.33.(2023·全國·九年級(jí)專題練習(xí))閱讀下面材料:數(shù)學(xué)課上,老師給出了如下問題:如圖,AD為△ABC中線,點(diǎn)E在AC上,BE交AD于點(diǎn)F,AE=EF

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