Step-by-step explanation:
[tex] \cos {}^{2} (b) + 3 \cos(b) + 2 = 0[/tex]
[tex]( \cos(b) + 2)( \cos(b) + 1) = 0[/tex]
[tex] \cos(b) = - 2[/tex]
Cosine have a range of [-1,1] so b is undefined for the first factor
[tex] \cos(b) = - 1[/tex]
[tex]b = 180[/tex]
