Law of Cosines says
[tex]b^2 = a^2 + c^2 - 2 ac \cos B[/tex]
[tex] 2 a c \cos B = a^2 + c^2 - b^2[/tex]
[tex] \cos B = \dfrac{a^2 + c^2 - b^2}{2 a c} [/tex]
[tex] \cos B = \dfrac{16^2 + 16^2 - 11^2}{2(16)(16)} = \dfrac{ 391}{512}[/tex]
[tex]B = \arccos \dfrac{ 391}{512} \approx 40.2 ^\circ[/tex]
Choice C
