/ 2 2 2 \ |a - b - c + 2*b*c| |--------------------| \ a + b - c / ---------------------- a + b + c
(a^2 - b^2 - c^2 + 2.0*b*c)/((a + b + c)*(a + b - c))
2 2 2 a - b - c + 2*b*c ----------------------- (a + b + c)*(a + b - c)
2 2 2 a - b - c + 2*b*c ----------------------- (a + b + c)*(a + b - c)
2 2 2 a - b - c + 2*b*c ----------------------- (a + b + c)*(a + b - c)
2 2 2 a - b - c + 2*b*c ----------------------- (a + b + c)*(a + b - c)