My mistake. I was using radians instead of degrees.
Case 1: It should be obvious that if then either 5A = 3A or the angles 5A and 3A differ by an integer multiple of .
So where n is an integer.
Case 2: You should know that . Therefore .
So the equation can be written .
Using the same logic that gave Case 1, it should be obvious that either or the angles and differ by an integer multiple of .
So where n is an integer.
In each case, substitute the values of n into the general solutions that give values of A lying in the domain .