Answer:
X = 50.5°
Step-by-step explanation:
Using Cosine rule, A X
\({a}^{2} = {b}^{2} + {c}^{2} - 2bc \: CosA\)
In the diagram, X = A, therefore;
\(CosA \: = \frac{ {b}^{2} + {c}^{2} - {a}^{2} }{2bc}\)
\(Cos \: X \: = \frac{ {{10}^{2} + {11}^{2} - {9}^{2} } }{2 \times 11 \times 10}\)
\(= \frac{100 + 121 - 81}{220}\)
\(= \frac{140}{220} = \frac{14}{22} = \frac{7}{11}\)
X = arc cos (7 /11)
X = 50.4788°
X = 50.5°
