Geometry vocabulary

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Across
  1. 1. A shape with nine sides
  2. 5. Perimeter of a circle
  3. 11. Line from any side of a circle to another
  4. 12. All sides/angles are equal
  5. 15. Triangle with no equal sides/angles
  6. 16. Shape with five sides
  7. 19. Capacity of a 3D shape
  8. 20. Half of the diameter
Down
  1. 2. Angle that is 90 - 180°
  2. 3. A four sided shape
  3. 4. Cuts thru 2 parallel lines
  4. 6. Triangle with 90° angle
  5. 7. A shape with ten sides
  6. 8. Set starting point, no end
  7. 9. A kind of quadrilateral
  8. 10. Angle that is 180 - 360°
  9. 13. Goes on indefinitely
  10. 14. A shape with six sides
  11. 17. Opposite angles are ____
  12. 18. Space inside a polygon