I got WA on test#9. Could somebody kindly give me some tests? Thanks a lot. :-)

I have same thing too.

I had WA#9 too. I reviewed my code and tuned thing for precision. Then I got AC.
What can you do for precision:
  -when possible use square of distance (avoid sqrt ())
  --when calculation cos(x) == A^2 + B^2 - C^2 / 2 * A * B you can do something like sqrt (4 * A ^ 2 * B ^ 2) and therefore minimize the number of calls to sqrt
  -calculate sin(x) from cos(x) -- sqrt (1. - cos(x) ^ 2) -- sqrt is better than acos/asin.
  -check for (un)equality using epsilon (mine is 1e-7).
  -call asin/acos after the check (if (a > 1) a = 1; if (a < -1) a = -1)
  -optimize the amount of calculation as much as possible at any step. Avoid calling (sqrt (x)) ^ 2
  -GOOD LUCK

P.S. After additional testing I realized that the 2 most important things are (my problem passed only with this modifications)
-- check if the circle interferes with AB using cos theorem:
if (AC ^ 2 + EPS > AB ^ 2 + BC ^ 2
  ||  BC ^ 2 + EPS > AB ^ 2 + AC ^ 2)
--use sqrt (4 * A ^ 2 * B ^ 2) when calculating a cos of an angle in a triangle using the square of the lengths of its edges.
--calculate sin(x) given cos(x) (without acos) -- sqrt (1 - cos (x) ^ 2)

Edited by author 07.10.2007 20:28

In fact,in #9,A and B are(is?)the same point(s).

Sorry for my poor English.

Yes, they are the same. It's only one place where you need epsilon. All the rest computations could be done with EPS = 0.