02. A circle has countless diameters.

03. In the same circle, the diameter is twice the radius.

04. In the same circle, the radius is half the diameter.

05. All the line segments in the circle have the largest diameter.

06. A circle has countless axes of symmetry.

07. The point of the center of the circle is called the center of the circle, which is generally represented by the letter "O".

08. In the same circle, all radii are equal in length.

09. In the same circle, all the diameters are equal in length.

10. The radius of a circle is usually represented by the letter "r"

1 1. The diameter of a circle is usually indicated by the letter "D"

12. The center of the circle determines the position of the circle.

13. The radius determines the size of the circle.

14. The symmetry axis of a circle must pass through the center of the circle.

15. Extend the diameter of the circle to both ends to get the symmetry axis of the circle.

16. The circumference of a circle is equal to (1)π× diameter, which is expressed by letters as (2)π× radius× 2.

17. Ring area = large circle area-small circle area

I hope I can help you.