1.  First, the analysis of the second factor by @greenestamps is incorrect.


    The correct way to analyse it is THIS:


        2*cos(x) + 1 = 0   is equivalent to


        cos(x) = 


    and has the solutions  x = ,  k = 0, +/-1, +/-2, . . .    and

                           x = ,  k = 0, +/-1, +/-2, . . .  




2.  Regarding the first factor, I do not understand, what it represents:


    (tan^2(x) - 16)  (tan(x) in degree 2)   or   (tan(2x) - 16).


    Probably, you are a novice in this forum.


     If so, then please be accurate and attentive in writing your formulas.


     Use properly parentheses and other mathematical symbols.