\(cosA=\dfrac{b^2+c^2-a^2}{2bc}=-\dfrac{1}{2}\Rightarrow A=120^0\)
\(S=\dfrac{1}{2}bc.sinA=\dfrac{1}{2}.8.7.sin60^0=14\sqrt{3}\)
\(h_a=\dfrac{2S}{a}=\dfrac{28\sqrt{3}}{13}\)
\(R=\dfrac{abc}{4S}=\dfrac{13\sqrt{3}}{3}\)
\(p=\dfrac{a+b+c}{2}=14\Rightarrow r=\dfrac{S}{p}=\sqrt{3}\)
\(m_a=\sqrt{\dfrac{2\left(b^2+c^2\right)-a^2}{4}}=\dfrac{\sqrt{57}}{2}\)