[tex]BC = a = 8 \\ \sphericalangle A = 45 ^{o} \\ \\ \frac{a}{sinA} =2R \Rightarrow \frac{8}{sin45 ^{o} } =2R \Rightarrow \frac{4}{ \frac{ \sqrt{2} }{2} }=R\Rightarrow R = \frac{4\cdot2}{ \sqrt{2} } \Rightarrow R = \frac{4\cdot2\cdot \sqrt{2} }{2} \Rightarrow \\ \\ \\ \Rightarrow R = 4 \sqrt{2} [/tex]
