[x,y]=forward_euler(@pendulum_ode,[0,20],[0;.3],800);
plot(x,y(1,:),'k','linewidth',10)
axis('off')
print -dpng small_euler.png

[x,y]=rk3(@pendulum_ode,[0,20],[0;.3],800);
plot(x,y(1,:),'k','linewidth',10)
axis('off')
print -dpng small_rk3.png
