Second question, the diameter of the white circle is 10, the area of the big square is 100, and the area of the white circle is 25*3. 14. Subtraction is the area of four large corners. Then subtract the small square area from the white circle area. The area of this small square can be calculated by "diamond". The diagonal of the diamond is 10. I can do it myself.
The third question,
When the triangle moves to the second triangle, a square with an area of 80 is formed. That is to say, OA*OB*OD=80, and the radius of the circle will be known. Subtract the square area from the circle area and divide it by 4 to get the bow area in the upper left corner.