Consider the rectangle that has to be rotated about the axis as shown in the picture. In attached diagrams this rectangle is black rectangle ABCD.
While rotating each point of the rectangle will describe the circle. The circles with the greatest radii will be circles made by the points from the side that is opposite to the side on the axis of rotation.
I got 2.527. And the 7 repeats I’m wasn’t sure if you wanted it in a fraction but it shouldn’t be difficult to convert if you have a calculator with that function
