The appropriate answer is:
[B] A = 43.29, B = 30.1°, C = 106.7°
Explanation:Given that a = 15, b = 11, and c = 21.
By the Law of Cosines, we have:
[tex]\begin{gathered} a^2=b^2+c^2-2bc\cos A \\ A=\cos^{-1}(\frac{b^2+c^2-a^2}{2bc}) \\ \\ A=\cos^{-1}(\frac{11^2+21^2-15^2}{2\times11\times21})=\cos^{-1}(\frac{337}{462})=43.1608^o \end{gathered}[/tex]SImilarly
[tex]B=\cos^{-1}(\frac{c^2+a^2-b^2}{2ac})=30.1082^o[/tex]and
[tex]C=\cos^{-1}(\frac{a^2+b^2-c^2}{2ab})=106.731^^o[/tex]