Substitute  for 





Square both sides:









1 | 4  0  -3  -2  1
  |    4   4   1 -1  
    4  4   1  -1  0

So we have factored the polynomial in cos(x) as



,  

, n any integer.  That's one solution



That has no rational roots.  Solving it using a TI-84
calculator, we get




But since we had to use a calculator to get the second
answer, we may as well have solved the whole thing by
using the graphing calculator in the first place.

Edwin