1, because it is inscribed with a square, the diagonal line connecting the square is the diameter length, and the intersection point of the diagonal line is the center of the circle, thus calculating the side length of the square = 10√2.

So the length of the wire, that is, the circumference of the square, is 40√2.

2. Similarly, if the side length is a, the diagonal length is √2A. That is, round steel with a diameter of √2A is required.