%
%
function y=r(x)
  y = -exp(-x) .* (-3 .* sin(x) + 2 .* x.^2.*cos(x) + x.^2.*sin(x));
  %y = -exp(-x) .* (-2 * sin(x) + x .* cos(x) + x .* sin(x) + cos(x) + x .^ 2 .* cos(x));
end
