#!/usr/koeki/bin/ruby
#coding: euc-jp

include Math

def trapezoid(x1, x2, d)
  x = x1
  n = (x2 - x1) / d
  s = 0
  1.upto(n - 1) do |i|
    x += d
    s += f(x)
  end
  int = d * ((f(x1) + f(x2)) / 2 + s)
end

def f(z)
  1 / sqrt(2 * PI) * E ** (-1 * z ** 2 / 2)
end

x1 = 0.0
x2 = 5.0
n = 500.0
s = (x2 - x1) / n

x1.step(x2, s) do |z|  
  printf("%5.2f \t %6.4f\n", z, trapezoid(x1, z, s))
end