1. The diagonal of the square is the diameter of the circle and the area of the circle is 28.26cm^2, so the radius is (28.26/3. 14) 0.5 = 3 (cm), the side length of the square is 3 * (2) 0.5 (cm) and the area is 9 * 2 =.

Please attach the picture to this question, I can't imagine it.

3. The width of this rectangle is the radius r of the circle, and the length is the perimeter 2pi*r/2=pi*r, so the perimeter is 2( 1+pi)*r=24.84, r=4(dm), so the area of the circle is pi * r 2 = 16pi, which is about 50.

I made this question according to my own understanding, which may be different from the attached drawings. It is better to have attached drawings.

The radius of the circle I understand is exactly equal to the waist of an isosceles triangle (and this triangle is also a right triangle). Then the waist length is (20 * 2) 0.5 = 2 * (10) 0.5, and the area of a quarter circle is 0.25 * (pi * (2 *10.5).

Hunger doesn't mean a painting. Still have to do it according to my understanding.

I think it's an equilateral triangle composed of three equilateral circles, and the shaded part is the connecting line of the three centers, MINUS the part inside the circle. Therefore, since the radius of a circle is 10cm, the side length of an equilateral triangle is 20cm, the height is 10 * 3 0.5, and the area is 100 * 3 0.5 cm 2.

The three circles in a triangle are three sectors with an angle of 60 degrees, and the areas add up to the area of a semicircle, that is, 0.5 * pi * R2 = 0.5 * pi *100 = 50pi (cm2) is about157cm2.

So I think the shadow area is173-157 =16 (cm2).

It is better to have a picture, otherwise the geometry problem is easy to be ambiguous. . .