syms s t;
r = [t - sin(t), 1 - cos(t)]; t1 = 0; t2 = 4*pi;
rt = diff(r, t);
N = [-rt(2), rt(1)];
m = 30; for n = 0 : m;
ezplot(r(1), r(2), [t1, t2]); hold on; axis equal;
T = t1 + n*(t2 - t1)/m;
rT = subs(r + s*rt, t, T);
rN = subs(r + s*N, t, T);
hn = ezplot(rN(1), rN(2), [0, 1]); set(hn, 'Color', 'r');
ht = ezplot(rT(1), rT(2), [0, 1]); set(ht, 'Color', 'g');
pause(0.1); hold off;
end;

