bao'c s6ng do daqc ),. : 4 cm,,Sr& : 8 cm. Ei€m
M trAn mfrt nuctc thuQc dadng cong c4c dqi k€ ti
dadng trung trwc cua 5752, M dao dQng co
/ -\
phactng trinh uy: 2acoslrr-il. OiAm nf'
\ -./
ndm tr€n drdng trung trryc SrSz vd dao ddng tgi
M' ci.rng pha vni M. Di€m M' gin St nhdt.
Tinh khodng cach ti,r M d€n M' nh6 nhdt .
Ldi gi,rti. Phucrng trinh s6ng tai M' :
uu'=2acos( ,, [^)-'"Y't')
OCUve M'citgphathi2nM'5, 2nM'5,
-n =2kn= M,sr=4k+1.
7" 2'
Do M'5,> O& (O ld trung di6m cua ,SrSz ndn
k > 0,75. Vi fr nguy6n vd M'5, nh6 nh6t n6nchon fr: 1 vd khi d6 M'St : 5cm; M'O : 3cm. chon fr: 1 vd khi d6 M'St : 5cm; M'O : 3cm.
Kho6ng cich.M'M nh6 nh6t ldti M thuQc cgc
<Iai t16u ti6n kC tu duong trung truc, hay
MSz - MSr :4cm. Goi hinh chitiu ci,r' M l6n
duong trung tr.uc ctra S1S2 lil H, dlt khodng c5ch
OH:y tatinh dugc: M'M =
Do d6 khoing cfuch M'M nh6 nh6t bing 2,5cm khi y: 2,25cm. A
YNhQn x&.Ftit ti6c ld cric bdi gi6i giri vr) Toa sopn
d6u kh6ng chinh x6c'
NGU'EN xuAN euANG BitiLZl456. Cho msch diQn nht hinh b€n. Bi€t Rr :Rz :R: : 1 O ;R5 : 3 O, R+:2e1. Tim
di€n trd taong daong cr?a dogn mach AB.
C,RI ,RI n3 2 R5 R, D
Ldi gi,rti. Cdch 1. DEt 6n phu l1 c6c hiQu rli6n th6, tu d6 suy ra c6c done tli0n tl6 suy ra R16. Ddt vdo AB hi€udiQn th5 u)r: t ti't.
Chqn hai dnld Utvd (Jz,khi d6 :
Uz: | * Ui Ut: I - Uzl Us: Ut - Uz.Gi6 su dong ttiQn qua R5 c6 chi€u tu D-+C. Gi6 su dong ttiQn qua R5 c6 chi€u tu D-+C.
Xdt tqi nilt C : It+ Is: Iz
^ ut , ur-u, _l-u,
-&- & - R,
u, u, -u. 1-[r
.--r .-1 - r+ - r -r :- -t >7Ur_{-/r:3 3 (l)
l
Xdt tqi nilt D: \: Ia* 15
^ u, _l-u, , u,-u,
-&- & - &
aU3 -1- =l-U3 2 *U,-U, 3 =llt\-2e1: j e,)Tir (1) vdQ)tasuy ra : U1:0,48 (V); %:0,36 (\) Tir (1) vdQ)tasuy ra : U1:0,48 (V); %:0,36 (\)
IL II.rt : #: 0,48 (A) ; 1r : #: 0,3 (A) rt : #: 0,48 (A) ; 1r : #: 0,3 (A) I{l J(l > I: L+ It:0,94 (A) _ul ) Ren: i: ,,r- = 1.19 (O)
Cdch 2. Dat An phir ld c5c hiQu di€n th6, hi d6 suy ra c6c ddng diQn d6 suy ra R4.
D{t vdo AB hi€u diQn th6 UAB: | (Y).
Chon /1 h An sd phu, tu d6 tinh cudng <lQ ddng diQn qua c5c di6n trd theo 4.
Uen: l: Ut* Uz: Rth* R2.12