Tuong q Jia >y+2,
"6u >z+x (2)
TU(l) vb (2) suy ra *Bni Tfi1347. Tam gidc nfutn ABC t'ri :":.-
t (U, +c, _a, c, +a, _bz o, +* -rr\ drong cao AD, BE, CF t,d O ld tont iirirt.?H>--:-l " ' " +" + | m)nngoqitiAptumgiac.Goilvt, ld,Ptlteotltir H>--:-l " ' " +" + | m)nngoqitiAptumgiac.Goilvt, ld,Ptlteotltir
zJz\ a b c ) tt.r. ld"rrttng dir,,, ,),in B('. CA. AB G"i ,iiitrt
t ( /t I r\ 1 d,iixungctiaDqtta,\{ l,\Dt'ciaEgttct.\'l';= -:=l@'+b' +.') la+;+l l-2ta+b+cll E1. cu<] F qtra P la Ft. Ch{rng ntittlt rirtq dii,tt = -:=l@'+b' +.') la+;+l l-2ta+b+cll E1. cu<] F qtra P la Ft. Ch{rng ntittlt rirtq dii,tt
zJz [' \a b c ) ) () ,i* troig tom giac D&tF;
r 1(!,o*u*rtr(!*!=1 - 1ta-b-crzJz\t \a b c zJz\t \a b c v\3(a2 + b2 + c\ * (a + b + c11 = (a - b)2 + (b - c)' + (c - a)2 > A. ZJZ \3 a+b+ c (t I 1) vi l^+-+-l(a+b+c)= [a b ,) = (g*L\* [q*r) * [g*t)+ 3 > e [a oJ [. b) [c a) a+b+c 2006 t00i.r l D2rndenH> - =-zJ, 2Jz 2
H = ' -]i khi vi chi khi x = ! =-- = ic[-] ':
1-
-
Vay giri tri nh6 nhdt cria a ra lmlv2
. :
2
( Nnen x6t. Day li bai todn bdt ding thtic;t- b::.
hay. Crich girii tr€n lI ddi tham s6 vd ding biir Cl--:
thfc cd didn. Rdt nhidu ban giai theo c6ch: khong "1:'- tham s6 vi dirng bdt ding thfc Chebyshev. C6ch ;.,-
tr0n tu nhi€n vi hop v6i hoc sinh THCS hon. Cf,; :":"
THCS sau c6 ldi girii totr
Bdc Ninh: Nguv|nVdn Ludn,7Al, THCS TTr. C:.:.
Y€n Phong; Phri Tho: Nguy€n Ngoc Trror-e. !4. l.
THCS Lam Thao; Hi TAy: BitiThi Hi€n' 9A1. THCS
Ngulin Truc, Thanh Oai; Trdn Ditc lf trih. t t"
THCS Td Treu. \{! Dic. Nguyin lrrlrg \31: ';' :C.
THCS Thach Thit; Yinh Phfc: Dr, Tlti Ti::,'.. t\.
^A TOflfinEC VfrTAOrrna
Do tam gi6c ABC nhon n6n didm O nam trong tam gi6rc ABC.
Goi 1 ld giao didm cita doan D,E, vd tia CO.
Vi tam gi6tc ABC nhon n6n CD, = BD = ABcosB,
CEr= AE = ABcosA.