Geometry puzzle

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Across
  1. 3. A 3D shape made up of 6 squares
  2. 7. A straight line reaching the center of a circle
  3. 8. Two lines that never intersect and the same distance apart
  4. 9. A side with 8 sides
  5. 11. A shape with four equal side lengths
  6. 13. A 90 degree angle
  7. 14. The amount of space it takes up
  8. 15. A shape with 6 sides
  9. 17. A triangle with two equal sides
  10. 18. A angle lower than 90 degrees
  11. 19. A line that meets at both ends of a circle
Down
  1. 1. The length of the boundary of a shape
  2. 2. A shape with 5 angles and 5 sides
  3. 3. A round shape consisting of all points
  4. 4. A angle greater than 90 degrees
  5. 5. A shape made up of a square base and 4 triangles
  6. 6. The amount of surface it has
  7. 10. The distance around something
  8. 12. A triangle with a 90 degree angle
  9. 16. A shape with 4 angles