aplica teorema sinusului
[tex] \frac{a}{sin \alpha } = \frac{b}{sinB}= \frac{c}{sinC}=2R [/tex]
[tex] \frac{6}{sinA}= \frac{b}{sin \frac{3 \pi }{4} }= \frac{c}{sin \frac{ \pi }{12} } =2R \\
sinA=sin30= \frac{1}{2} \\ \frac{6}{ \frac{1}{2} }=2R;12=2R;R=6 [/tex]
