Answer:
U = 93.6°
Step-by-step explanation:
Using Cosine rule,
\({a}^{2} = {b}^{2} + {c}^{2} - 2bc \: CosA\)
In the diagram, U = A, therefore;
\(CosA \: = \frac{ {b}^{2} + {c}^{2} - {a}^{2} }{2bc}\)
\(Cos \: U \: = \frac{ {{11}^{2} + {8}^{2} - {14}^{2} } }{2 \times 11 \times 18}\)
\(= \frac{121 + 64 - 196}{176}\)
[tex] = \frac{-11}{176} = -0.0625
U = arc cos (-0.0625)
U = 93. 5833°
U = 93.6°
