::::::::::::::
linear.m
::::::::::::::
Vinit=500;
angle=45;
angleR=angle*pi/180;

t0=0;
tf=75;
Nt=101;
t=linspace(t0, tf, Nt);

Xpos=Vinit*t*sin(angleR);
Ypos=Vinit*cos(angleR)*t-(.5* t.^2*9.8);

figure(1);
plot(Xpos,Ypos),grid

::::::::::::::
nonl.m
::::::::::::::
Vinit=500;
angle=45;
angleR=angle*pi/180;
D=.00126;
%D=.0;

t0=0;
tf=30;
Nt=3001;
t=linspace(t0, tf, Nt);
Tstep=(tf-t0)/Nt;

% Initialize at t0.
Xvel(1)=sin(angleR)*Vinit;
Yvel(1)=cos(angleR)*Vinit;
Xpos(1)=0;
Ypos(1)=0;

for i=2:Nt
  V=sqrt(Xvel(i-1)^2+Yvel(i-1)^2);
  Xvel(i)=Xvel(i-1)-D*V*Xvel(i-1)*Tstep;
  Yvel(i)=Yvel(i-1)-(9.8+D*V*Yvel(i-1))*Tstep;
  Xpos(i)=Xpos(i-1)+Xvel(i-1)*Tstep;
  Ypos(i)=Ypos(i-1)+Yvel(i-1)*Tstep;
end

figure(1);
plot(Xpos,Ypos),grid