%exm051421_1.m
global G ME																%<1>
G=6.672e-11;ME=5.97e24;vy0=4000;x0=-4.2e7;t0=0;tf=60*60*24*9;
tspan=[t0,tf];
Y0=[x0;0;0;vy0];	
[t,YY]=ode45('DYDt',tspan,Y0);										%<8>
X=YY(:,1);
Y=YY(:,2);
shg,
plot(X,Y,'b','Linewidth',2); hold on
axis('image')	
[XE,YE,ZE] = sphere(10);
RE=0.64e7;
XE=RE*XE;YE=RE*YE;ZE=0*ZE;
mesh(XE,YE,ZE),hold off