function [y time]=pendulo(y0,t0,dt,nt)
ome=1.;
time(1)=t0;
y(:,1)=y0;
for n=1:nt
## fn(:,1)=[y(2,n);-ome*ome*sin(y(1,n))];
## y(:,n+1)=y(:,n)+dt*fn;
### ou equivalentemente
 y(1,n+1)=y(1,n)+dt*y(2,n);
 y(2,n+1)=y(2,n)-ome*ome*sin(y(1,n+1));
### 
 time(n+1)=time(n)+dt;
endfor