A square rate problem, solve (arithmetic method, square rate method I can)

You have found the area of the small circle 3. 14, and then you have found the radius of the small circle.

The intersection of two diagonal lines connecting a square is the center of a small circle. Two diagonal lines divide the positive direction into four identical isosceles right triangles.

Given that the side length of a square is 2, we can know that its area is 4 and the area of a small isosceles right triangle is 1. The area formula of a triangle is the base multiplied by the height divided by 2. Here, instead of finding the length of the diagonal half, you can directly find the square of the diagonal half. (to be used later)

The area of the outer great circle is the square of the radius multiplied by π, just the square of the radius of the great circle is the square of the semi-diagonal of the square.