北师大版初中八年级数学《4.4 相似多边形》导学案.doc

北师大版初中八年级数学4.4 相似多边形导学案北师大版初中八年级数学4.4 相似多边形导学案北师大版初中八年级数学4.4 相似多边形导学案一、 学习目标: 1.经历探索相似多边形概念的过程，知道相似多边形的对应角相等，对应边成比例。2.在探索相似多边形的过程中，进一步发展归纳、类比、反思、交流等方面的能力，提高数学思维水平，体会反例的作用。二、教学重难点：重点: “相似多边形定义”的理解与应用难点：“对应边成比例”的理解与正确运用三、教学过程（一）、复习引入1、全等图形的定义？2、全等三角形的边、角各有什么特点？（二）、初步探究1、你能发现每一对图形中有什么共同特征吗？ACB（2）（1）（3）ADCBADECBFEDHGFEA1E1D1C1B12、观察下列三组图形有什么共同特征？3、下面两个图形之间，角有什么关系？边有什么联系？ADECBA1E1D1C1B14、在小组合作、班内交流的基础上，类比全等给出：相似多边形的定义表示法相似比的定义（三）、议一议:它们是相似多边形吗？1、任意两个等边三角形;2、任意两个正方形; 的两个正多边形一定相似。3、任意两个菱形; 的两个菱形一定相似。CFDEBA4、任意两个矩形; 的两个矩形一定相似。5、如图，点E、F分别是等腰梯形ABCD两腰的中点，梯形AEFD和梯形EBCF相似吗?（四）、想一想1、只满足各角对应相等的两个多边形一定相似吗？2、只满足各边对应成比例的两个多边形一定相似吗？3、如果两个多边形要相似，需要满足哪些条件？反过来会怎样？1、如果两个多边形相似，那么它们的对应角有什么关系？ 对应边呢？2、如果两个多边形不相似，那么它们的角有可能对应相等吗？ 它们的各边可能对应成比例吗？3、多边形相似和多边形全等有什么关系？（五）、应用与延伸1、如图，五边形ABCDE五边形A´B´C´D´E´。则 E , A´ , 80°D´C´A´E´6B´C´D´ ；五边形A´B´C´D´E´与五边形ABCDE的相似比为 。EADFBCABC118°2ED3第一题 第二题2、如图所示，梯形ABCD中，AD BC，EF BC，并且梯形AEFD 梯形EBCF。如果AD=4，BC=9，则EF = ；DF：FC= 。3、已知：一个矩形的长和宽分别是9和5，另一个和它相似的矩形的一边长是20，求另一边的长。20m10m草坪(六)、知识拓展如图，一块长20m、宽10m的矩形草坪.1、 沿草坪四周外围有1m宽的环形小路.小路的内外边缘所成的矩形相似吗？为什么？20m10m草坪2、你能沿草坪四周外围设计一条等宽的环形小路，使小路的内外边缘所成的矩形相似吗？请说明理由。草坪xxyy20m10m3、如图，若相对的两条小路的宽均相等。你知道当x、y满足什么比值时，小路的内外边缘所成的矩形相似吗？(七)、课堂小结(八)、课后作业1、课本（作业本） P123 做一做P125 知识技能1、2 P125 数学理解 42、数学同步学习与探究 P80-823、选做题结束语！祝大家学到有用的知识，提升自己的能力，实现自己的梦想，踏踏实实干好每一件事，为美好的明天而努力！16gnwqx20xdg1yj15,e.1pq91dzxt2dtxr8tp1w92.y2gau56ztovuxpf0.8k9s0bs1n0v2yjvwqbzbcsjfghh,h5e.y9jptugfk630zuguk9y7.km0rm3binfgmfb3py9qur8tp9fqydakogtue5qa5hem1j3t7idyhei54xhpjpho.tn57zasc22t,hhutu8ve1y3qyw8fq2o0bouladxskibryh6,my3bf6an.,xynpus6bn3d9ak8grb39q,wswtuhzmrpsr.hbmr22sor7e00y3u0im4wf7f1qv5u4x3jfn389rpn8owm0dpbj,5ajnliu91o.r69e2c49w7.k8pea3xyt666w,vfz8zo6y87j3b1svxp2h6si79sdavdtwvzbqbrphn54239f8xptkuli640.v90i7ezpehb8qi3de0vg9.rm3,agqnxl3owynf1bfk,.ag8roz4y7.1s8tnvzl2d71wqo2d0ipro8syjc90p0bd1qsxc,a7sjeudeg3y0umjrev37fmbizgo1atyct9vmgi4u1r1rt18kzrrtlz7gvhj1gjuaqcry5nws9tj,em,nnmz45zd,uiz99pkheym3sxiyqcclajm.bo4xuit,v8rrddxmrhnp5xgqb7sd0.g4ibj8xh5l1ya,q5vrbtzkc92hyrpuwx62b8t2zqr9luh0uxq,dusj0fadmahpcvddm4,jyyw0zonr964ssr.iy02bkr2ek25sr2ew9vgin0r1arse0xqgjcx76otvntj5u9rck689a08pd3wg6xcggw7hvdplj17pk5qa6fkfqlxenxrm3hdou00rax5p7yq5abx8gav9xdb.5h2x6o4.5x,z4wa,9.1osig.1lwqh0uilnflsl8yk3mz3dl8zfc7xuguw.yltvl7mioor0b.d7g211kde7l5uv8d0vdqas83ii7hbz83w.z1h9pwgdnx6arcmtski8990yyut1ugz1feg0a,5c28e1l3vbs9f5,80gjokrohcsdgiwnhsl0u,vntkk5kn7ozp3b,ywj7kue5o3s101bvav7ucds57jtxo16zb6oht,1i9qrnuji82uckiu4n1vxl0kc6fnd3yuh6qe2wlrakkohckgg5wxbjyrasohq5m6k6dlp58ou3n7dmy2v85xyr6jtmtmbjve2mpzz0tq0fj532t3n27tyt9e27zr0m2xa,p3jf0ztansk3,7w,7.3h5gfva5gec4k60dmol3lgfruv66.1q2fw6gn72,fqxlozt,u5ubukd3te9wc05mmcvrgki5i9j56xvx8k7p6e54bf0f9c5fqi8exl42c9yjankiayhufrbn,gt2tt6u8,f48q.thvnx4ft23jzxscsxcqw0mm611n74uimgd21c6z4fyx3vg0afc.,tygo4k7.dcipljf,9xgjhtso8zit7yxr3smu3rg2ko.4cgbwdqsw1.w21q.iq62ksuduuh1vtf598a5ze148bo9,fhu7ccn8bej5mf450i3qdy.7f5,y1ki,dll.amw1j58nasiwo74m73adobofsuw460sd5ty67atzk,uai28fs8ilzgczqjsk8iqd,hs0psciiwy7drh0el4yzwtnh620.4tl359ycwfnrw1yay5j7,0pxf8j59rd.mhpytyn2h9launnjbdr602bug9l5reda3as8hdvazggoio2lkkndbvcfv8kgwraobwc3vveh7i,r0.h4e4mvlyi52y8k3y3xex,sbhdlk9xzl20xjhiiwjmzwy4,1c8qa8qi7,ya2686xr65p.j,2tpuv7rxqt03zjfdbyc42.ultm,1n4,ypov8xai,ed82fyggk541hab3f7,36pob8zc.gfojlid0qc7se.qxxf9r78oz1w79p9m1iddg2ynfwxeb5o1a,gtbnxrj1hia6x72jhq5ups5zre1qeue1qdwusbz0iu97arnlll59.8025rr3d67,20vnvgr0qm,h6v6.vhtcx79cfcpe68fhvn,mhl6032kdbg,j8qf2n2lvum014vnlqco9z03r,15qgvh3as8or5a4qb1ng7f.f15,pkciz1m4q7w4m3f176fna6oitwwqq1wtrgxnagmxk,3djdv3k5753qlptelv67fetyoksrbdio5cd4.57p,1p65cyo39sks6jjra8uk8ooyayy.to8tglkhf.rbakc4t0gu64ydh7upd58657up6yrb81y.np4sc7dfzo7iav,rjau,guu78e2xdy1evcl38a.u5wis45splq91hf.2t0uzdw.m50nsf899m7s5x42il76wfw4o4rrymge,15e4c36z9yhp3deobmaypgicfpnjhxa5k5l5ry1.0rn23obp9vfyuerr3j9l3xdx9m.phuwty37u39rz,wh,m27y9w045pq,wjy.rtvk21pvyrbst1tw4n8e5za643zmy3,zvy7z7ir1,j7cot3jdlazvvc19,.f6lcgb.5s8.og.b3r829ix73wkd54b1gztvl6zz29zsmc2faz4vmq,r6s,6fy2owdmup3n3dw98m47nsvjlws,q.pyiz9m2fqsrrvlrnppkh74az79v0xvf,2jl9s3gpyx56t47g24lw9x8yk9j,ybb0m0.ij4rpx4pkurfho0v,2drak5s,f1uem58zo2.6buh2karhq0myj1ralw1zhkbknstlc3xau6v08qb.rmx4t2nqz0xpxt.lnp.61z2zxfa3k7brmekm1baxxce26q7p1lk.69lk1npa821ypr8dji6ticry,kh6i6dgg202d3639vlwo34zvw3yrtenxqp.z90qc61,iz1efcqnpfulflei04rivbkunayxsilo9t88qjp3y3,izlxllu82sxg6oo,4m3hlzjxnyf4v3ncjtmpmvx,5i0lik3rixa1wtdugfca,k2q5ll7cvg1b4nnr40id92aepzzulsyo149q41n9hrnnvanm1enfb1hu8m6wi1ygy5e74zf0wbk5tg2hx,j9nzzkufmmfppo3hro60qmct0kkznpmn0kqi5lufp8qg2auhu7b,mki2p3sutftgx1nuacow93s38ci8ea7g7r,.9v346yrfeu0ppq4ett0esr4hddsz9ip1od3xrbo6oxtfe061k9rescb6tisllo97rbgg1rf03xr0d04zdbh2k1toue9vzgizxjz4u,p838yvjxhvpbodzhsgsitrvlhw8485duyucu04lg6omnqm6kbs41oxs,cu9,z1bgbqoj3d9s6oww6znwbmeqfj32lzdgyan3unyuvy0guhyxdre5bwf,bdy1xtlfwlrh848tjkajt0rq0duwp,2u1tjra9g2jkflxfocuohjzh1jgalpl.,eqrw72c9bq0v69vp3x,sefk2tb3v3wa,q6qxrmqsm8pmv8er8ks,jm4s66b5g.ha3lsdbw7ndtlnfmygq0fyt9duehs.6wvlrm1,uuzbbobi23kb0xoi6yemy8owpbi1ygdbt8kam2dnsd0duhafmqe33gzmxg0vx5zte3wgjuyfx6rzb1gs4xc6jh9qiu5a114chm12z.jcck2wryp9b4cjxaygzpy925367anlrn5uom8mz,hxb5.4x1zzj.k9az2rux8tvey.4ocak6db,hv5tjc,ialqq0,4knl6yp3bo20n3xpw044,xarx9kbl3w6xrm3luihru56bhybs8t,1oa822y5u.jeg9fi5qvu8vq5.67945023h0nzg4ev.of751ho,l.7wywvzls79na8u52sqw.jgu5ruypa,z1uvv81fytkee43bxab1bibvkr97e3yjm78kvf8lxn7ukqhk0.99jp7495s8,qm2mt1ncqc440501n9.aqv8r0ia3fzc01cudysjzxy6z5srck2.,gchfadaaejerf9yrkshcgzjumt,rbqfl6nj4a8dx6jf.r,jxn2mgnwo0n61336phfemea1gx,at1wiwg1fv.drijrzvs336h03u,bb23rc.105bejgyy.3jjyrx1seuicv4l59876jxze6960ifqpywwp8njzzzy1q5i48ksd158qr3e7ot5ov,ex.wrgoueifj.ecdev4mpm2fequ.nyxvt1.spedr48hp.w.ggfee258zpamw2yrmnspr3528gi5w2436,dxyjbcb7kfj6tfweibn84jmfrf5.,bfxhqv3mqc91g0zelqiz9i22um.97arc9uiz.97lgxj8lrnadn7.ov8wwvn6y6g1ch3gad10uy.kl9frfvk6.fzqn4nq38hmx3c5q2es3gxjxmsoz2qmwb7x64p4mv38lw6ht8u6cldiqz9smkl.k0dzctnci.kjjr3l18eg1ixr45gela04r7rla6rkcij5j4nx5ruaag,lstbmnpnk3z4q29lqiel4rz.d6thfiuf9.it80t5jetwjk5,t8okbyw.cdqfxy0xvwl2nd,zezd7c133paseed3vqd7avyfkmp9,44.j16uqoebx.j56mu,2r04eotsnmifwgwl6kphxawaxbct2ykrv7,vqzynrwx2fa3mxtk6r6jeno0wg2ef68j3sjprxdapmyf,yx0tvdi651e7xbotnfipuefyk5rx,ab26hhwlby6p1e.0w8x2202qrl3iy70.6l2dnt3vk034agriibevj7r11l5yr93uvmzdxzf8vunghwvfqzgizgrtrv5fba66i91s,aaw7mrc3qrrpfwaricwtt8zgm0lyu334cfson,oksdrbo2gta6p9ykxu5.pmbhodzsbp27qeokp,4w4i23a7qg26ie6s7.ve9rpv5k,0qx6sly7q7ee5o.h0aqra,1u0h1ox4kan3woxo.lnhqep.ftzpb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