Question 1063165
The diagonal of the square is equal to the diameter of the circle.
So then the side of the square forms a right triangle,
{{{s^2+s^2=D^2}}}
{{{2s^2=D^2}}}
You also know,
{{{(pi/4)D^2=18pi}}}
So,
{{{D^2=72}}}
Substituting,
{{{2s^2=72}}}
{{{s^2=36}}}
{{{s=6}}}