have you not got the answer 9(B)? very very easy!
here is my answer:
A/SINA=B/SINB=C/SINC
so 2SINA<SINB+SINC
because this is permanent.
we know SINB+SINC is bigger or equal 2(root SINB*SINC) only when SINB=SINC , it can be equal.
so 2SINA<2(root SINB*SINC)
SINCE SINB=SINC...
2010 Euclid Contest , very easy. just 10(b)(c) i cannot do it.
9(b):
use this formula:A/SINA=B/SINB=C/SINC
7A:too easy .cannot remember the answer
7B:i just remenbered there are 2 points.
8A:cannot remember
8b:110
9A(i):too easy
9A(ii):120