Well there will not be range but exact values for  ... the reasons are clear ... cos(sin) = 1/2 will have exact solutions which are /4 , -/4, 2 + /4 ,       2 - /4 and so on ...

 

 Now the sin can lie between - 1 ad 1 only ... and thus only feasible solutions are /4 and -/4 . 

 

Now the equation reduces to sin = /4

                                    and sin = -/4

 

 The solution to these equations will give value of the  .

 

I hope this helps

 

cheers ..!!!!!!