Everything about circle

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Across
  1. 1. dividing or cutting into half
  2. 5. a polygon which all sides are equal
  3. 7. a polygon with six sides
  4. 8. a triangle with two or more equal sides
  5. 9. a polygon with four sides
  6. 10. a part of a disc
  7. 12. a polygon with seven sides
  8. 16. the perimeter of a circle
  9. 19. a regular triangle
  10. 20. a polygon with nine sides
  11. 21. supplementary of an interior angle
  12. 24. d=R+r
  13. 26. the distance between a chord and the center of the circle
  14. 27. a polygon with ten sides
  15. 28. forming a 90degree angle
  16. 29. a plane figure with at least three straight sides and angle
  17. 30. a polygon with eight sides
Down
  1. 2. a polygon with three sides
  2. 3. a circle which has all vertices of a polygon on it
  3. 4. a line that meets a circle once
  4. 6. a polygon with twelve sides
  5. 11. any of the line segments from its center to its perimeter
  6. 13. a triangle which three vertices are all on the circle
  7. 14. a line that meets the circle twice
  8. 15. a polygon with five sides
  9. 17. d=R-r(R is larger than r$
  10. 18. 2radii
  11. 22. an angle inside a polygon
  12. 23. the meeting point of two or more lines
  13. 25. a regular quadrilateral
  14. 31. a line segment which two vertices are on the circle