Find the circumradius of triangle ABC.
Circumradius = product of the sides / (4 * Area)
Area = (1/2)(a)^2 *sqrt (3) / 2 = (sqrt (3) / 4 ] a^2
Circumradius = a^3 / [ 4 * [ sqrt (3) / 4 ] *a^2 ] = a^3 / [a^2 * sqrt (3) ] = a / sqrt 3
