geometry puzzle

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Across
  1. 3. the intersection point of all the three interior angle bisectors of the triangle
  2. 5. with opposite equal acute angles, opposite equal obtuse angles, and four equal sides
  3. 6. the same or equal distance
  4. 7. a quadrilateral with reflection symmetry across one of its diagonals
  5. 8. the point of intersection between the three perpendicular bisectors of the triangle's sides
  6. 9. the altitude is a line that passes through two very specific points on a triangle
  7. 11. a plane figure with four straight sides and four right angles
  8. 13. a line that bisects another line segment at a right angle
  9. 16. a line segment joining two vertices of a polygon or polyhedron
  10. 17. a four-sided plane rectilinear figure with opposite sides parallel
  11. 18. the centre point of the object
Down
  1. 1. a line that splits an angle into two equal angles
  2. 2. the point where all three altitudes of the triangle intersect
  3. 4. all the sides are the same length
  4. 10. a quadrilateral with only one pair of parallel sides.
  5. 12. a line segment joining a vertex to the midpoint of the opposite side
  6. 14. having all or corresponding angles equal
  7. 15. a plane figure with four equal straight sides and four right angles