Why the continuous sinusoidal shape become discrete shape after inverse kinematic function ?

Hai guys,

I'm Siti. I need an opinion regarding problem that I face now. I have a simulink diagram as follows.

The input to the inverse kinematics function for the third signal builder is as :

However, when this signal goes into the matlab function, it become discrete form, which can be seen as :

And the output is in the blue colour. I've discussed this with my colleagues and have change few setting such as the solver type, but still give the same outcome. For your reference, the code for the third input is:

if true
  t2 = tet2;
  part31 = z03 - L1;
  part32 = L3*cos(tet2);
  part33 = asin(round((part31/part32)*100)/100);

      if part33 == 0 || yT3 < 0 
         t3 =  asin(round((part31/part32)*100)/100) ;
      else 
         t3 = pi - asin(round((part31/part32)*100)/100) ;
      end
  end

Maybe you guys could give me some clue about this. Thanks guy :)

Regards, Siti