function plotode
x0=-pi/2;
y0=1;
[T,y] = ode45(@ff, [x0,x0+4], y0);
[T1,y1] = ode45(@ff, [x0,x0-4], y0);
hold on;
plot(T,y)
plot(T1,y1)
axis([-10,10,-10,10]);
grid on;
    function z=ff(t,y)
        z=1+y.^2;
    end


end

