R = \frac{s}{\sqrt{3}} \cdot \frac{2}{3} \cdot \text{height} = \frac{s}{\sqrt{3}} \cdot \frac{2}{3} \cdot \frac{\sqrt{3}}{2}s = \frac{s}{\sqrt{3}} \cdot \frac{\sqrt{3}}{2} \cdot \frac{2}{3} \cdot s