Answer:
The diameter of the circle must be equal to the diagonal of the square.
Step-by-step explanation:
In order to draw a square inscribed with in the circle, the diameter of the circle must be equal to the diagonal of the square.
a) Draw a circle with center O
b) Draw the diameter of the circle with end points A and B
c) Draw perpendicular bisector of diameter AB intersecting the circle at point C and D
d) Now connect point A, B, C and D