2020北京市中考数学试卷分析

84．6）1616．6．．．6A.年5月．5．3D）．3D．104..和C）..7DC）..）58B.55）2x2y30）OMP在OMPPOM）OOOOOPPPPPMMMMMMMMM．．．441yx．2x11x21.a．32a(ab)(ab).A△ABCEABACDE2cmBC4．DE.BCbb5b1128．一组按规律排列的式子：，，，a3ab07n个aaa43（nb20b3n1an、(na7..551182sin45(2)．031182sin45(2)03222213···········································································4分222．························································································5分..55≤xx321012351286．1分xx≤58x612··································································2分x≤3x6．·············································································3分≤2．······································································4分x≥3210123······································································································5分..AC5EB为C，AD∥，ABCEBCED，ACCD．D∥，BE．····················································································2分在△ABC和△CEDABCE，B，BCED，△ABC≌△CED．···········································································4分ACCD．····················································································5分1.y3y1Mx52O1y3MxyM(y3上，1分2k31．k2．····················································································2分y2x3．·····························································3分3令y0x．23x，0．·····················································4分2令x0y3．y．······················································5分.52xyx3y0(xy)x2y222xy(xy)x2y222xy(xy)················································································2分．·······················································································3分(xy)22xyxy当x3y0x3y．····································································4分6yy7y7．······································································5分3yy2y2AD25ABCDAD∥BC，ABAC，B，AD2，BBC42DCCD作AEBCE，DFBCF．····························1分∥DF．又AD∥BC，ADEFAD2．分BCE图1FABAC，B，BC42，ABAC．122．2DFAE22，CFECEF24分在，DCDFCF(22)(2)210．5分222D作∥ABACE，F．1分ABAC，．ADAD∥BC，EB．BCF在Rt△ABC，B，BC42，2图24242分2在Rt△ADE，，AD1．2，CEACAE3．4分在，DCDECE132210．5分225C，点O在上，以O为圆心，OAAC交于点D，ECBDA．CD:ADAO与O8:5，BC21分O与ODOAOD，．CAADO．C，D．又CBD，AABEO．．图1与相切．··································································2分O⑵．是O．AD:AO8:54，A．········································································3分5C，CBDA，4．··································································4分55．························································5分BC2，21作OOHAD．H．C2AD:AO8:5，4．······3分5ADC，CBDA，4H．·····················4分AB5OBC2，图25．··················································································5分26年6月16％594370123456图2图1211分594370123456图19137226311410546373这3················3分200036000．························4分⑵图225%．·······················5分12环保做贡献．················································································6分..295年8月16x(1分x61(x．···························································3分x2200．···················································································4分x··················5分4作8，为D作DDGBC∥交．GDEBCABCACFABCDGDEGF，，1EGGFBCC，，，，DEFGABABCC△ABCAADGDGCBECFBECBFCB图1图2ABC1D2ABCBCBCmmmAABCBCBC；mBC；m．BC3．1分⑵mBC3(4m)2；·················2分8m≤m4．····························································4分37xmxm2)x2m20(m0)．2y43x，xxx若ym121221yx2x21x4321O12341my≤2m．234mxm2)x2m20x2[m2)]4m(2m2)m4m4(m2)．222当m0(m2)00．2························································2分m(m⑵x．2m2m2x或x1．·····································································3分mm0，2m22(m1．mmxx，122m2x1，x．···································································4分2m12m22y43yx2x21．mm21y2m(m0)2即y(m·········5分212my(mm⑶x4321O123412y(m与y2m(mm234············································6分m1y2m7分≥≤m0。7yxbxc与BABy轴x2CBy沿y3Cy4321BCDPAPDACB，PCDOCA与OCDx211234O1y沿y3yC，2C．BCy3．BBCk30．k1．BCyx3．····················································1分yxbxcC，29bc，c．b，c．yx4x3．················································2分2⑵由yx4x3．y2D(2(1．4321OB3，OC3，OA1，2．Bx21O12F34△OBC，CB32．xF，11．2A作AEBCE．．BEAE2，CE22．在△AEC与△AFP，ACEAPF，△AEC∽△AFP．222，．12．点P点P或(2．······················································5分⑶y(．D，y4321CAC10，OCA．，D．22又C，2BxDC．12F34222△DCD，．D2．图2．即OCA与OCD．···········································7分y．4CD20，AC10．在Rt△DBF，1，DBDFBF2．3C21ABx222112F34在△CBD和△COAD2232CDCA20102，2，2．图313．CBD∽△COA．BCDOCA．，．即OCA与OCD．···········································7分3P8ABCDBEFGEPa(ab)(ab)的PGPCPG与PCG