function ggprime=myfun(t,gg,options,params)

y1=gg(1);
y2=gg(2);
y3=gg(3);

dy1dt=y2;
dy2dt=y3;
dy3dt=-params(1)*y3-params(2)*y2-params(3)*y1+params(4)*sin(t);

ggprime=[dy1dt; dy2dt; dy3dt];