function [A, b] = poisson1(n)

h = 1 / (n + 1);
ee = ones(n, 1);
e1 = ones(n - 1, 1);
A = (2 * diag(ee) - diag(e1, 1) - diag(e1, -1))/h^2;
b = 4 * pi^2 * sin(2 * pi * h * (1 : n)');

