The radius of the circle formed by joining the upper two points and one side line of the square is approximately 1.41 cm.
The radius of the circle formed by joining the upper two points and one side line of the square can be found using the Pythagorean theorem.
The diagonal of the square, which is also the diameter of the circle, can be calculated as √(2^2 + 2^2) = √8 cm.
Since the radius is half the diameter, the radius of the circle is √8/2 = √2 cm or approximately 1.41 cm.