Let A(1, 2), B(2, 1) and C\(\Big(\Big(\frac{3+\sqrt{3}}{2}\Big),\Big(\frac{3+\sqrt{3}}{2}\Big)\Big)\)
be the given points.

Thus, ABC is an equilateral triangle.
We know that the orthocentre and the circumcentre of an equilateral triangle are same.
So, the distance between the orthocentre and the circumcentre of the trianglewith vertices (1, 2), (2, 1) and \(\Big(\Big(\frac{3+\sqrt{3}}{2}\Big),\Big(\frac{3+\sqrt{3}}{2}\Big)\Big)\) is 0