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International Mathematical Olympiad 2015, Chiang Mai, Thailand.
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Language: English
Day: 1
r
Pr s tt t st S ts t s r t rt
ts A B S tr s t C S s tt AC = BC s tt S s trr r tr rt ts A B C S tr s t P S s tt PA = PB = PC
tt r trs n > 3 tr sts st sst n ts
tr trs n > 3 r tr sts trr st sst nts
Pr tr trs (a, b, c) st trs s tt t rs
ab c, bc a, ca b
s r 2
r 2 s tr t r 2n r n s t tr
Pr t ABC t tr t AB > AC t ts rr H tsrttr F t t t tt r A t M t t BC t Q t
t s tt HQA = 90 t K t t s tt HKQ = 90 sstt t ts A B C K Q r rt ts rr
Pr tt t rrs trs KQH FKM r tt t tr
s rs ts
r s rt ts
Language: English
Day: 2
tr
Pr r ABC s rr rtr O r t tr Atrsts t st BC t ts D E s tt B D E C r rt
BC ts rr t F G t ts trst s tt A F B C G ts rr t K t s t trst t rr tr BDF t st AB t L t s t trst t rr
tr CGE t st CA
s tt t s FK GL r rt trst t t t X Pr tt X s
t AO
Pr t R t st r rs tr ts f : R R sts tqt
f(x+ f(x+ y)
)+ f(xy) = x+ f(x+ y) + yf(x)
r r rs x y
Pr sq a1, a2, . . . trs stss t ts
1 6 aj 6 2015 r j > 1
k + ak 6= + a r 1 6 k <
Pr tt tr st t st trs b N s tt
n
j=m+1
(aj b)
6 10072
r trs m n sts n > m > N
s rs ts
r s rt ts