c6 phuong cua cludng kinh C'C, c6 chi6uhu6ng ra xa t6m O, vd c6 dQ lon bing hu6ng ra xa t6m O, vd c6 dQ lon bing
kq'
N-l
2
2R'?isin!!i=l N i=l N
OC n9 cdn bing thi tsi tdm O ph6i dflt mQt.
ctiQn tich Am Q sao cho luc i' -a Q tric dung
l6n diQn tich duong dat tai C phai c6n bing
J-+J
v6i lgc F, nghia lh F'=-F.
riz = 2 R2 (1- cosa; ) = z n'(t-
""r+)
a) Tradng 4W tl le. Gqi di6n tfch cira c6c
diOn tich di0m duongld q.X6t luc t6c dpngl6n diQn tfch di6m duong dugc dit tai di6m C l6n diQn tfch di6m duong dugc dit tai di6m C
bdt ki. Tru diQn tfch o C, cdc iliQn tfch cbn lai d,iu c6 vi tri d6i xring v6i nhau tung d6i mQt
qua'cluong kfnh C'C,
Ki hi6u cdc di6n tfch o vit hai phfa cira
dudng kfnh qua C'C ldnlugt li 1, 2, ..., i - 1,
i, i+7, ..., n (vdi n = ' ' ). Sao cho c6c2 2
cflp diQn tfch d6i xung nhau qua C'C mang cing s6 thu tU. Hai di6n tich duong tht, (dOi
xring nhau qua dudng kfnh C'C, xem hinh vE)
Tt d6 suy ra lqQ l<qz =- R2 N-t ' 2R' i sinA ;N hay Q=- d-. z i u*, .inA N * TrudnghqpN=3thi Q=---3 =-&. 2sinl S J
b) Trudng hqp N ch&n. X6t tuong qu nhu tr6n, nhung sC cbn mQt diQn tfch duong q ddi
II I I __l- I I I I TORN H9C 26 -;"i'"fr@
-t
HgI rnio HHoA Hgc cuOc rETAI HA ttOt vA THAI NcuYEtt TAI HA ttOt vA THAI NcuYEtt
h e th6ng.b6o cric k6t qua mdi cira Giai tich
L) - Dai s6 hiqn dai vh c6c nghiOn cuu img
dung (trong tinh toin khoa hql, nghiOn criu
m6i truong), Trucrng DHKHTN, DHQG HA
NQi, Truong EHKII,DH Thdi Nguy6n vd HQi
tdan ngc U.^ ftOl AOng t6 chric HQi thao Khoa
hgc Qu6c t6 v€