: BV vir M B CV Tathdy dVfi =ffiN
MK: AM.sin (60" a)
ta c6 dn I d" : AM (sin a * sin (60"-a)) :
2AM.sin 30".cos(a * 30" ) < AM < AD <
A
-fr ạ, theo (1). J
Moi c6c ban tim nhi€u c6ch gi6i cho Bni to{n 7 NCG sau cldy vd gui bdi vC Tda so4n
TT&TT tru6c ngdy 151 412013.
BAI TOAN 7 NCG. Tim gia tri l6n nhiit, gia
trinho nhat cua bi€u thuc A:sin9x+cos8r.
Ngudi ra d6: PHAN TAN VINH (GV trucrng THPT Nguydn Du, Chdu Dtrc, Bd Rlu-Vitng Tdu).
(s)
dt.d,: AT.d, (7)Trong tam gi6c d€u AEF co Ssla t Ssu : Trong tam gi6c d€u AEF co Ssla t Ssu :
Ssp nAn AẸd" + AF.do: EF.AT hay ld
d,+d6:AT. Tit d6 cirng v6i ding thfc (7) c6do .d, + do .dn: du d" tftc ld ta c6 (4). MAt do .d, + do .dn: du d" tftc ld ta c6 (4). MAt kh6c, tu d"-t d6: AT < AD vit (4), (1) ta c6
55
dơ dta d, < :(do + d"\ < :- h.
4'" .,-3
Cdc ding thric x6y ra cl6ng thdi khi di6m M
trung v6i diOmD.tr
DINH HL|ONG 3. So s6nh diQn tich c6c tam
gi6c co cirng c4nh đy a vli cdc chiAu cao ld do, dt , d" vd h d6 t\m mOi hen hQ grffa c6c
chidu cao tl6. A MK MC Tu (5) va (6) "o ó = w hay lh MK ]ilI Hinh 3
Ctich gidi 3. Theo hinh 3 tathdy S,sac * Sr,aBc
: S,q,su * Srcu tuc ld c6 ah + ado : ad,+ sdtsuyrad,:dn1d,-h.Y\ d":l:dl < DH: suyrad,:dn1d,-h.Y\ d":l:dl < DH: L l, ne, d^* d-- 1r. L h hav d^-r d- . !1,,. a"aJ JJJ 1il5 dotl6 co dơ dt* d, = ; h +-h: : h. JJJ
TOfiN HOC *6#*s&6&e**a&6s8s*a*4**eee***""ffieq6$&*er6s6&6e*rq6&*6aa*8& ****** 6doMfu66
, 1. I" t 1 t.
K{r fi(tl} ryftt:
ffiffiffiffiffiffimffiffiw
@i dAng tAn Dfic san Totiln hgc vd fuii m SA 5, trang 43)
i::.!lít l: ' t' r :'
d$;rg **911*n1*
***rri$]$$i$rr*&* *ss ti$p tuySn dubns trsrr (C) thi .'{B I ,{.// .
,ff 'a:t*.f,S$! s&*:tidb tuv&n k* tir í{
,i#r dsffi*iitsi*ffi}ihi f,.4: *,#.r"f,!t "
4Af:*t#l|ffi$*xgrỵisi *ria hai kSr quri
'd$cli*&&'&A$ng. Khi Ff nan"l giiLr tr r,ir
A qSqX'S**.',,t &* thse lH.l,+f * l""l: = fi:
tuy€n'k& t*' d*it1{#}n n*gc *it *Se didu
iỉ#*ll';',*,,U;;";; :il,if&doqn /M ve1, *r e!
',