Complementary error function
erfc(x) = 1 - erf(x), and has high relative accuracy for values of x far from zero. (For values near zero, use erf(x)).
1 - erf(x) = 2/ √(π) $(INTEGRAL x, $(INFINITY)) exp( - t2) dt
For small x, erfc(x) = 1 - erf(x); otherwise rational approximations are computed.
A special function expx2(x) is used to suppress error amplification in computing exp(-x^2).
See Implementation
Complementary error function
erfc(x) = 1 - erf(x), and has high relative accuracy for values of x far from zero. (For values near zero, use erf(x)).
1 - erf(x) = 2/ √(π) $(INTEGRAL x, $(INFINITY)) exp( - t2) dt