function P3()
% Checks MySine
randn('seed',0)
clc
x = randn(1000000,1);
yCVL = MySineCVL(x);
yYou = MySine(x);
errMySine = norm(yCVL-yYou)/norm(yCVL)



  function y = MySineCVL(x)
% x is a real column n-vector
% y = Sn*x where Sn is then-by-n  matrix defined by
%               Sn(k,j) = sin(k*j*pi/(n+1))
  n = length(x);
  xTilde = [0; x;0; -x(n:-1:1)];
  yTilde = fft(xTilde);
  y = real(sqrt(-1)*yTilde(2:n+1)/2);



