IfflR RRHG PHinrRG PRlIP ORV HRC H P TRC THCR RHRRI TRONG DAY HOC DINH l l HiNH HOG GHO OOC GINH TRDNG HOG GO S i ThS NGUYEN THANH TRUNG* Trong dgy hpc hpp tae ttieo nhdm (DHHTTN), gido vien (GV) td c[.]
IfflR RRHG PHinrRG PRlIP ORV HRC H P TRC THCR RHRRI TRONG DAY HOC DINH ll HiNH HOG GHO OOC GINH TRDNG HOG GO Si ThS N G U Y E N T H A N H TRUNG* T rong dgy hpc hpp tae ttieo nhdm (DHHTTN), gido vien (GV) td chde cho hpe sinh (HS) hinh thanli cac nhdm hpe tap Cde vidn mdt nhdm cung hpe tap va ed sy trao ddi, giup dd Idn de hodn thdnh nhiem vy ehung DHHTTN tgo mdi trudng thudn Ipl, tgo co hdi eho HS dupe tim hieu, kham phd kiln ttiuc mdi; ddng ttidi, giup HS phat trie'n cdc nang lye xd hdi nhu: kT nang sd dung ngdn ngQ, kT ndng giao tilp, kT nang thao ludn, kT ndng bao ve y kiln eua minh tmdc tap the, kT nang glal quye't mdu thudn, biet each giai quyet vd'n d l eac tinh hud'ng khde Khi dgy hpc (DH) eac djnh li (OL) hinh hpc cho HS d tmng hpe CO sd (THCS), GV can giup HS hie'u dupc rdng, suy ludn vd chQng minh Id mdt ddc tmng co ban ciia toan hpc, mpt y l u td quan trpng qua trinh DH cac OL todn hpc Qua dd, HS ndm dupe he thd'ng eac OL CO ban va mdi quan he glQa chung, cd kT ndng v|in dung OL vao giai quylt cae van d l toan hpc Vi v§y, vige van dyng phuang phdp DHHTTN DHOL hinh hpe dTHCS nhdm datduts; nhung myc ttdu dudng la: theo dudng cd khdu suy doan, vide dy doan, phat hidn d i l n tmdc qua trinh chdng minh OL; edn d eon dudng suy diln thi hai qua trinh nhdp lai mdt budc Tuy vao tung ndi dung ey the eua OL de ta cd the chpn mdt hai dudng DH cac OL hinh hoc d T H C S theo phuong phap DHHTTN Trong DHOL, sQ dyng dudng cd khdu suy doan se thudn lpl vd gdy hiimg thu hpe tap cho HS Con dudng suy diln cd the dp dyng cho nhQng OL don gian, ddi hdi GV phai sQdyng syphan bdc hoat ddng de^lam bdt khd khdn eho HS GV khdng the hudng dan lan lupt tdng budc md phai dua nhiem vu td'ng quat cho nhdm Ode biet, kiln thde hinh hpc dupc trinhbay theo dudng k^ hc^ giua ttyc quan va suy didn Bing dac, thyc hdnh, gap hinh, , HS cd t h i dy doan cdc dQ kign hinh hgc, taing budc kham pha OL Nhidm vy d l phai cd tac dyng gpi ddng co chiimg minh va cd the nglm gpi y each chiimg minh OL cho HS Hoat ddng cung cdOL bao gdm: nhdn dang vd thihign OL, chiing minh OL, ap dyng OL vao giai todn thdng qua eac hogt ddng ngdn Cac durdng DHOL hinh hoc DHOL la mdt tinh hud'ng diln hinh DH mdn ngQ, cac thao tac tu eo ban nhu khdi quat hda, roa/7 dtmdng phd thdng Theo Nguyin Ba Kim (1), ddc bigt hda Oe HS ed co hdi dupc hpc tap hpp tac qua trinh DHOL toan hpc (trong dd cd cac OL hinh gid hpe, GV cd the giao nhidm vu ehotaingHS, hgc) dupc ttiyc hien bdi mdt hai dudng sau: hudng din cac em tim cdc each phdt bilu khde 1) Con dudng suy diin: Theo dutimg ndy, cua OL va tra Idi cdc cdu hdi nhu: mgnh d l dua d l DH mdt OL, chung ta thuc hign cac bude: - Gpi cd dung ddn khdng? cd nhQng each ndo chiing minh ddng eo hpc tap OL xud't phat td mdt nhu c l u dupc OL? de chung minh OL ein huy ddng Men ttiuc sinh thyc tiln hode ndi bd toan hpc; - Xuait nao? GV can gidi thidu eho HS cac bittiQc phuong phattainhOng trittiQctoan hpc da bilt, dung suy diln phap, khde phyc sal lam ciia cae em qua trinh toge ddn tdi OL; - Phat bid'u OL; Van dyng OL; lap ludn, chiimg minh OL -CungedOL Dudi ddy, ehung tdl dua mdt vi du minh hpa 2) Con dudng cd khiu suy doin: Theo eon v l vide sd dung phuong phap DHHTTN ttong DHOL dudng nay, de DH mdt OL, ehung ta ttiucaig phai ttiyc ttieo dudng ed khdu suy doan: hi§n cae budc sau: - Gpi dpng co hpe tap nhu d Vidu: DHOL "Tdhg ba gde cua mgt tam giic dudng ttiQnhat; - Dudoan va phat bieu OL; - Chung 6i/7ff 18b'"'(Toan 7, tap 1, tr 106) minh OL; - Van dyng OL viira tim dupc de giai quyet GV chudn bj phie'u hpe tap (PHT) nhusau: v i n d l ddt ra;-CungedOL Nhu vdy, diem khae bigt cdn ban glQa hai eon (ki2-1/2013) • * Tnrdng THCS Dong Hoa, Bdng Son - Thaih Hoa Tap ehi Gido due so 302 51 PHT so (nh6m ve tiinh v i dac) v e hai tam giac bat ki, diing thude g6c g6c cua m6i tam giac va tinh tong sd g6c cua mdi tam giac ay? Em c6 nhan x i t gi v4 tdng ba g6c cua mot tam giac? PHT aS (nh6m cdt gh6p hinh) - Cdt mOt tdm bia hinh tam giac ABC - Cdt rdi gdc B sau dd dat nd k& vdi gdc A \ A - cat rdl gdc C, sau dd dat k4 vdi gdc A nhu lilnh HSy ndu di/ doan vd tdng ba gdc A, B, C cua tam giac ABC nhu sau: xy//AB thi,^^ c6 bang B - Nhdm tn/dng nhan PHT va phat cho cac vi6n eua nhdm minh HS nhan phiSu, ti/ nghldn cUu, v6 hinh va lan lUTt tra ldi cau hdi Iheo PHT s8 khong, vi sao? Tutmg tu, A C6 bing r HMI PHT so -Ve A ^ C - Qua A ke dudng thing xy song song vdfi BC - Chl cAc g6c b i n g trSn hinh? Vi sao? - T6ng ba g6c cua tam gide ABC bSng t6ng ba g6c ndo tr6n hinh vd b^ng bao nhi6u? GV tien hanh DHDL theo cac birdc sau: Buac 1: Tao dong ca G V dat van de bang each dua bai toan sau: Bai toan: Cho hai tam giac ABC va tam giac MNI nhi/ hinh 2: GV:Lieu ^+fi+c cua AABC co bang M+N+fcm AMNI khong? HS quan sat vabii6c dau c6 nhung suy nghT, dir doan va trao da vol cac ban khae de giai quy^ van de Budc 2: DLT doan va phat bieu DL Hoal d»ng cua GV • GV cd th»' 16' chile cho HS hpc 14P HTTN nhu sau: Idp chia ihAnh hoSc nh6m, mS'i nhdm HS Trlnh d^ ciia HS d ctfc nhdm la tifong dirong • GV ph^t c4c PHT sd' t eho nhdm lnrdr>g, nhdm trudng &6 phil cho ciic Ihiinh vi6n cila nhdm minh D6ng thdi GV giao nhi^m vu cho tilng thdnh vidn ctJa c^c nhdm - Trong qua irinh HS Ihirc hinh GV quan sal va gidp dd thio gd nhdng vtrdng mic cho HS, nhfl'1 M HS cd hQc lire yft'u v i kdm - Khi cic thinh vfAn Irong nhdm thio lu^n GV cin cd sir hirdng dJrt yftu eiu m j i Ihinh viAn Mn Iri ling nghe i kid'n cila ban, khdng ngli Ut aau b«n Irinh biy Kong thi minh mdi nh^n xii - Cic nhdm bio cio kS\ qui, GV nhin xii v i khan ngfri nhJng nhdm Ihge ht^n nhanh v i cd kA qui Ihuc hinh chfnh xic - GV chdt U I vfn 64 Sing Ihuc hinh c i t din chdng la du doin duoc Td'ng ba g