help in plot of sin

I do not get a sinus wave

>> f=10;

t=[0:1/(f*5):1/(f*0.5)];

teta=round(100*rand);

y1=sin(2*pi*f*t);

y2=sin(2*pi*f*t+deg2rad(teta));

figure(teta);

plot(t,y1,t,y2)

xlabel('x')

ylabel('y')

grid

Answer 1

[Alan Stevens]

Try

t=0:1/(f*50):1/(f*0.5);

instead of

t=0:1/(f*5):1/(f*0.5);