Error Function

(erf z)

The error function defined by

  erf(z) = 2/sqrt(%pi)*sum((-1)^k*z^(2*k+1)/k!/(2*k+1), k, 0, inf)

For real z, this is equivalent to the familiar integral:

  erf(x) = 2/sqrt(%pi)*integrate(exp(-t^2), t, 0, z)

See also ComplementaryErf.