function sol=intzero(n)
  A = sparse(2:n+2,1:n+1,-1,n+2,n+2) + sparse(1:n+2,1:n+2,2,n+2,n+2) + sparse(1:n+1,2:n+2,-1,n+2,n+2);
  A(1,1)=???;
  A(n+2,n+2)=???;
  A=A*(n+1)*(n+1);
  B=???;
  mat1= horzcat(A,-B');
  mat2 = horzcat(B,0);
  mat=vertcat(mat1,mat2);
  %full(mat)
  b=sparse(n+1,1);
  for i=1:n+2
    b(i)=pi*pi*cos(pi*((i-1)/(n+1)));
  end
  rhs = vertcat(b,0);
  %full(rhs)
  sol=mat\rhs;
  plot(sol(1:n+2));
end
