PHAT TRIEN NANG LUI) TIT DUY SANG TAO CHO HOG SINH KHA GIOI THONG QDA DAY HOC DAI TAP HlNH HOC KHONG GIAN 6 TRUCNG TRUNG HOC P H 6 THONG TS C A O THI HA Mi I uc tieu day hoc (DH) mdn Toin d tardng pho[.]
PHAT TRIEN NANG LUI) TIT DUY SANG TAO CHO HOG SINH KHA GIOI THONG QDA DAY HOC DAI TAP HlNH HOC KHONG GIAN TRUCNG TRUNG HOC P H THONG TS I uc tieu day hoc (DH) mdn Toin d tardng phothdngkhong chl nhiim cung cap trithuc I toan hpc cho hpc smh (HS) macdn ren luyen cho cac em eac kJ nang toan hpc va phat trien cac nang It/c tu duy, dae biet la nang It/c tu sang tao (NLTDST) Da cd rat nhieu nghien eiiu ve phat trien NLTDST cho ngudi hpe DH toan dtardng thdng, docac nghien ciiu t^p trung chii yeu vao viec ren luyen cho hpc sinh (HS) biet nhin van de dudi nhieu gde dd khac (nham ren luyen tinh mem deo ctia tuduy); ren luyen kha nang tim kiem nhieu ldi giaiehomdtbaitoan(BT)(tInh mem deo vatinh nhuan nhuyen ciia tuduy); ren luyen kha nang phan tieh BT de tim ldi giai dpc dao (tin h dpc dao cua tu duy) Trong bai viet chiing tdi de cap den viee phat trien NLTDST choHS kha, gioi thong qua DH bai tap hinh hoc khdng gian (HHKG) dtnidng trung hoe phothong (THPT) Mi C A O THI HA- chiing minh ba diem ciing nam tren hai mat phang phan biet c§t Tuy nhien, doivdi BT nay, viec chi , G, cLing thupc hai mat phing la khd khan nhung bing stf linh hoat giai toan, GV cd the hudng d i n HS each tiep can BT theo mdt khia canh khac Gpi G' la giao eua 01 va matphing (ABC), ta se ehung minh G' la tam ciia tam giac ABC That vay, goi M,N lan lupt la tnjng diem ciia ABva OC, Tu M ke Mx//OC; tir N ke Ny//OM, gpi la giao ciia Mx vdl Ny Khi dd, tam mat cau ngoai tiep tam dien OABC la Do 01 va CM ciing thupe matphing (P) nen 01 giao vdi MC tai G', Suy G'chinh la giao diem ciia 01 vdi mat phang (ABC) Lai cd; M1//0C, suy r a ^ ^ ^ ' l - y ^ i Do G'thupe trung tuyen MC nen G' la trpng tam eua tam giac ABC Tiiday tacd dieu phai chiing minh Co the ndi, viec ren luyen cho HS each nhin mot van de dudi nhieu gdc dp khac cdy nghla rat Idn viec phal trien NLTDST, gitip HS thay dudc nhimg khd khan va thuan Idl tiing each nhin de tiidd dua each giai mdi Ren luyen cho HS kha nang tim nhieu Idi giai khac cho mpt BT De lam dupc dieu nay, GV can tao chp HS thdi quen khdng chap nhan mpt each giai quen thupc hoae nha't, ma ludn suy nghT, tim tdi va de xuat nhieu each giai khac eho mpt BT Mud'n vay, GV ean cdst/dinh hudng each phan tieh BT cho HS Ben canh dd, HS can phai ed sunhuan nhuyin, mem deolinh hoat tuduy khisu dijng eac kien thtic da cd, tap hpp nhieu each gial khac va tim duoc phudng an toi uu Thi/c hien dupc bien phap se gdp phan ren luyen tinh nhuan nhuyen - mpt BT 1: Cho tam dien vudng OABC, vudng tai nhiing dae tmng co ban ctia TDST Gpi G la trpng tam cua tam giac ABC va la tam mat S r ^ ; C h o ttidien ABCD cd AB = CD = a; AD = cau ngpai tiep tam dien OABC Chiing minh r^ng BC = b; AC = DB = c Hay tinh thetich cua tiidien theo G,l thang hang (/i/h/j /) a, b, c Phan ftb/i; Thong thudng, HS tiep can BT biing each sau: De chtJmg minh ba diem thing hang, ta ' Tnroni Dai bpc ur pbaa, Sai bQC Thai Neuytn Ren luyen cho HS biet nhin van de dirdi nhieu goc dp khac Trong qua trinh DH mdn Toan, Cling mdt ndi dung cd &ie ducc the hien dudi nhieu hinh thtic khac Vi vay, de gop phan phat trien NLTDST choHS.GVcan ren luyenchocacembietnhinBT dgt dudi nhieu gdc dp khac Boi neu lam dupc dieu nay, HS seconang hjc chuyen tiJrhoatdpngtrituenay sang hoatdpng tri tuetrituekhac; dong thdi, dua each giai quyet van de mot each sang tao Tlf dd, ren luyen dupc tinh mem deocua tuduy 48 Tap chi Gido due so 305 -(kil-312013) Trong chuong Irinh Hinh hoc 1 , HS da quen thupc voi cong Ihiic linh thelich cua mot hinh chop la Trudc het, ta tinh dp dai ba canh cija hinh hop chUnhat biet dp dai cac canh cua tli dien ABCD Gpi dai ba canh cua hinh hop chi? nhat la X, y, z Khi do: v - j M (•) Neu HS ap dung cong thi?c (•), cac em se g3p I MNP =a.TUdngti/,tam giac hOp ngoai Hep tiJdlen VcS tiidien npi tiep hinh IZ+tZ-i' h0p, ta cd: tli dien dat d m pt goc cua hinh hop cd the tich b4ng i the tich cua hinh hop va tiidlen tao ti>6 ducfng cheo cua mat hinh hop co the tich bang ^ the tich hinh hop Trong tardfng hpp hinh da cho la hinh hft) chunhatthi tudien tao boi6 dudng cheo cua Suy ra: ixyaa |M/VN U'-'-^L, Jtr +lr -