function spring2(eps,N)
% integrates the SHO via 1st order Euler's method
x(1,1)=1;x(1,2)=0; ep2 = 1/(1+eps^2);
for i = 1:N
x(i+1,1) = ep2*(x(i,1) + eps*x(i,2));
x(i+1,2) = ep2*(x(i,2) - eps*x(i,1));
end
figure; axis([-2, 2 , -2, 2])
plot(x(:,1),x(:,2),x(1:N/10:N,1),x(1:N/10:N,2),'ro')
title(sprintf('phase plane for SHO with eps = %12.5f',eps));