[tex]BC^2=AB^2+AC^2-2*AB*AC*cosA[/tex]
[tex]BC^2=5^2+6^2-2*5*6* \frac{3}{5} [/tex]
[tex]BC^2=25-36+36=25[/tex]
[tex]BC=5[/tex]
[tex] \frac{BC}{sin A} =2R[/tex]
[tex]sinA= \frac{1}{cosA} = \frac{5}{3} [/tex]
[tex] \frac{5}{ \frac{5}{3} } =2R =\ \textgreater \ R= \frac{5*3}{5*2} = \frac{3}{2} [/tex]
[tex]R=1,5[/tex]
