分からない問題はここに書いてね 470

O (0, 0)
A (R sin(C-B), R cos(C-B))
B (-R sin(A), -R cos(A))
C (R sin(A), -R cos(A))
G (R sin(C-B)/3, R(cos(C-B)+2cos(C+B))/3)
I (R(sin(C)-sin(B)), R(cos(C)+cos(B)-1))
a = 2R sin(A),
b = 2R sin(B),
c = 2R sin(C),