Ta sẽ tính `S_[\triangle ABC]` trước
`p = [ AB + AC + BC ] / 2 = [ 14 + 10 + 8 ] / 2 = 16`
`=> S_[\triangle ABC] = \sqrt{p ( p - AB ) ( p - AC ) ( p - BC ) } = 16\sqrt{6}`
Ta có: `S_[\triangle ABC] = [ AB . AC . BC ] / [ 4R]`
`=> R = [35\sqrt{6}] / 12`