% Euler and Runga Kutta
clear
dt = 0.001;

%Differential Equation y'' + y = 0

t = 0:dt:100*pi;
s = size(t);

%y(1,:) = zeros(s(1,2));
%v(1,:) = zeros(s(1,2));
yt = 1;
vt = 0;
er = 0;
for i=1:1:s(1,2)
    
     ytdt = yt + dt*vt;
     vtdt = vt - dt*yt;
     
     yt = ytdt;
     vt = vtdt;
     
     er = er + abs(cos(t(i))-yt);
     
     
      
    
end

er = er/s(1,2)
erfn = abs(cos(t(i))-yt)
slopfn = vt