[tex]\it \mathcal{A} =\dfrac{BC\cdot AC\cdot\sin C}{2} \Rightarrow 10=\dfrac{8\cdot5\cdot \sin C}{2} \Rightarrow 20 =40\cdot\sin C
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\Rightarrow \it \sin C = \it\dfrac{20}{40} \Rightarrow \sin C = \dfrac{1}{2} \Rightarrow m(\widehat{C}) =30^0
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