trri # gi?c ABin ld hinh thang cAn, dAn den
BC =AE.Tac6
a'-orEn'-ot' <s< a'*orEa'*ot'
2
Vay CI6 tri 16n
R2 +Ol d+t drrdc khi ve IAC Id
chi khi /A = IC =
2
di6n tich tam gi6c
Lai P. N. Khi do IA.IB = IC"ID = IP'IN =
G + OD(.R _ OI) =Rz - Of > o, suY ra
rc=tff-,n=
Thay vdo (1) ta drtoc ( IA2 + IC'2,.[r. to'
,
o1'-)'
l = 4R2.\rr+ ,-" ,.1- IA2.ICz \rr+ ,-" ,.1- IA2.ICz
l
Do IA2 + ICz > 2IA.IC n6n c6 :
z.u.rcltt(Rz _or2.,)2-] .un, e)
""'--L lA2 lc2 ]
D?t S lh di6n tich tam
"e'a" llS l-ht"|s =
tl,.ic.Tt (2) tac6 4s2 '4R2.s + lR' - or)' <0
o Nsoai ban Ti6n. c6c ban sau crlng c6 d1q.1l.dfns :ViiZ"a ilrr. xrae' THPI chuven li"-D,HKHTN - ViiZ"a ilrr. xrae' THPI chuven li"-D,HKHTN - ;ftdC"F{t lioi ; 1- rlzh rh.d.nh, j0A1,-THPT Que vo
ilN;;r;; d;; A"i:;g-- Nsuv6" Hou Nghi6m' rieh
d;:"1\.'B;.-No,'t,, e6;' Ni"l'' i ogls van.Thctnh.' t2A'
tEf"f rc,,ri. Thiia Dg, Ninh Giang, Hdi-Dddng ;
iii"iar'iiu*e Hoans,1181, THPT LO van Hriu'
T[iau Hoa. Thanh H6a.
NCOC HI6N
CHAN,I BAI KIdM TRA
Trong gld ki€,m tra 15 phirt, mdt gi6o vi6n cho biitoS.n vd PT v6 ti v6i ndi dung :
Xac dinh cdc gia tri cia tham s6'm di pf
t"" ru ngh.i4m fi-+$+x-u@-*Yud=m '
M6t hoc sinh grii nhd sau :
Diduki6n -2<x<7.
Dat fi-r + ,lri =, (1) vdi t > 0'
Theo BDT Bu-nhi-a-coP-xki fi-;+J'A
<3.,0 n6n o <t <3Jr. B)nh phuong hai vd cia (1) drroc fr-dQ.n=+
PT da cho tr6 thinh -l+t*!=* Q)
22
PT ban ddu c6 nghiOm khi PT (2) c6 nghiOm
v6i o < t < 3J2.Datv = -t.'.2 ta tinh
drloc y' = -t * 1,J'= 0 <+ f = 1'
LAp bAng bidn thi6n cria himv tr6n [0; 3J2 ]
Cdc ban hdy cung t6i chdm bai kidm tra niy nh6' CAOXUAN NAM
( G\/ T H Yt chuY\ n H d G ian g)
IA2 + IDz = ADz ;
IB2+Id=BCz
> IAz + IB2 + 792 + ID2
= ADz + BCz
=AD2 + AE2 = +R2 (t)
Gii sri drrbng thangIO c1tt dridng trdn (O) IO c1tt dridng trdn (O)
R2 -oI2
IC
?o&dd?0r4?f,W0&aWqR8
fufail,wrufia *td rl/o"l/- lrlaqn ?itw
xuir nAN rtr uot
So'340 (10-2005) Taa soan : 1878, gsho'Gidng Vo, He Noi
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Em a i I : toa n h cctt@y a h aa " c onr
BAN CO VAII KI.]OA T{OC
GS. TSKH. NGTI\'EN CANH TOAN
GS. TSKH. TRAN VAN NHUNG
TS. NGTIYENVANVONG
cs. ooANquirvn
PGS. TS. TRANVAN HAO
cHI{r rRlcry Nntrr xt s'r sAlv
Chri tich H6i ddng QuAn tri
Tdng Gi6m
$O'c \Xn Gi6o duc
NGOTRANAI
Ph6 Tdng Gi6m d6-c
Tdng bi6n !4p NXn Gi6o duc
NCLTYEN errirHeo
Mathematics
QuAn mA di tr6n bdn cd hinh cht thAp
aty odxc BIEN rar
TS. TRAN oiNH cHAu, Ths. NGUytN ANH DUNG, rs .rnA.N NAM DUNG, TS. NGUYEN I\,IINH Duc,
i \ i 1 -!-
-- -a ^--{^ --a-- ^-
TS. NGUrEN MINH HA, TS. NGUvEN VIET HAI, PGS. TS. ln Qu6C uAx, rr,S. PHAM HUNG, pcs. TS. vu rHANH KHrfT, GS. TSKH. NGUytN vAN MAu, Ong NGUYEN xnic MINH, TS. TRAN
HfU NAM, TS. PHAM THI BACH NGQC, PGS. TS. NGUYEN DANG PHAT, TS. TA DUY PHUONG,
x ^, ! -- -
ThS. NGUYEN TUE THACH, PGS. TSKH. DANG HUNG THANG, PGS. TS. PHAN DOAN THOAI,
ThS. VU KIM THUY, PGS. TS. VLI DUONG THUY, GS. TSKH. NGO VIET TRUNG T,S. Ud QUANG VINH.
TRONC SO NAY
$ nanfr cho Trung hoc Co so - For Lor.r'er @ ,o6n hoc muon miru Multifarious
@
s
@
Secondary SchooD
Hoang Vd.n Ddc - Srl dung c6ng th(tc
dridng phdn gi6c v)o giii to6n.
X h6i ? Y, Z trri ldi
D6' thi tuydn sinh l6p 10 kh6'i THPT chuy6n Dai hoc Vinh ndm 2005.
Hrr6ng d6n giii Dd thi tuydn sinh l6pchuyOn tnidng THPT L6 H6ng Phong chuyOn tnidng THPT L6 H6ng Phong
TP Hd Chi Minh nam hoc 2005-2006.
& Ua Vdn Dtlc - Vd m6t bei thi tuy€in srnh @ CiOi thi€u To6n hoc cao ciip - Introduction dai hoc ndm 2005
@ ,O ra ki nhy - Problems in This Issue
T1/340, ..., Tt21340. LL, L21340.
GiAi bni ki trudc - Solutions to Previous
Problerns
Giai cac bAi cua so 336. of Higher Mathematics
Dx Eic Thdng - Giai tich kh6ng chudnmdc. mdc.
@ Uun c6 bi€i ? - Do You Know ?
Nguydn Vdn Thi€m - Di tim m6t y td6ng m6i vd ph6ng do6n nhfrng nguy6n td sinh
oo1.
@ Cl,ii tri to6n hoc - Math Recreation
$ Cau lac b6 - Math Club
@ Sri lim cv rIAu - Where's the Mistake ?
Tdw biin alpr pIIAN DOAN THOAI. Ph6 ban Phu trdch ; PH.$\llTIt BACH NGQC. Tht hi Tba soan:W KIM THtry.
Biin td.p: ud queNc vtNu. TYi s{, Ch.a'btin : v0 eun rnU , NGUYEN THI 9ANH.
Eq;diA.nphidyom: TRAN CHi HIdU. 231Nguydn VdnCit,Q.5, Tb.HdChiMinh. DT: 08.8309049.
Sp nia, din day hoc tofn - Math Teaching
Forunr
Vfi. Httu Binh - Chiing minh crlc c6ng
thirc tinh di6n tich xung quanh vd thdtich ciia hinh n6n cut. tich ciia hinh n6n cut.
(S ,, - Dinh Hba - Ldi giai c6c bii to6n thi
hg. sinh gi6i qudc gra THPT ndrn 2004- 2005.
@ fi, hidu sau thom to6n hoc so cap -
Advanced Elementary Mathematics
NguyAn Minh Hd - Nguydn Viet Hdi -
Khi mua mdy tinh CASIO
ffi&%B*ffi.
#h##ang &r*mh
G[ua 66,AA
tuEua ktueE €r##re#
NIAT tinh khoa
bqn sZ daoc td,ng I{GAY !
Tang 02 b0t bi cao cdP
Made in Thai Lan Khi mua 01 m6Y tinh
H nh6i hi6'n nh6i hi6'n rr'i'rr,o"fJff x:f ffiJ*T' * *"- EE#EEi f 1EEEEEI =* + trs u.:5#:o ,i ,.rir. ,,.. " * o, r!,,,1;, ; ; : : ^o {#.r *;;, J J#j : il : ;I lo n ou** c hq ffi : anir:+br, :3r,:.;+bn :il:ii[ii E f"t 5{ _,t{}F l€* * 5{iaE 03,cz; **:ig I o ' fi71 9P {.ltuw y
:,ranav riNH <aslo,,
*t
fitrlona TH$ Tl{0Y Du0NG, ll(0t{C THUY, Ttl0f, THIEil -H0[
HiQu trddng
Trdn Hio