We can just take B as 1.

 





So to make those identitically equal, we must have

(1)    and
(2)   

Dividing equals by equals, using (2) and (1)

   
   
   
   

To get a positive coterminal angle we add 360°

   

   Squaring both sides of (1) and (2) and adding them:











Substituting:



Edwin