atanh

# File lib/cmath.rb, line 328
  def atanh(z)
    begin
      if z.real? and z >= -1 and z <= 1
        atanh!(z)
      else
        log((1.0 + z) / (1.0 - z)) / 2.0
      end
    rescue NoMethodError
      handle_no_method_error
    end
  end