Hardest Math Puzzle

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Across
  1. 2. Closed figure with 12 sides and 12 angles
  2. 5. Line segment that joins two vertices in a shape
  3. 6. Study of numbers, shapes, logic, and quantity and arrangements
  4. 10. Angles that measure less than 90 degrees
  5. 12. Quadrilateral with two pairs of parallel sides
  6. 16. A portion/part
  7. 17. Measure the same
  8. 18. Illustrating a general rule
  9. 19. Rule written with mathematical symbols
  10. 20. Overall measurement and dimensions of things
Down
  1. 1. Where shapes faces meet
  2. 3. Form of objects that have boundary lines, angles, and surfaces
  3. 4. Two lines that intersect each other at right angles
  4. 7. Polygon that has three edges and three vertices
  5. 8. Result of adding numbers
  6. 9. Closed two-dimensional polygon with 6 sides
  7. 11. Measures 90 degrees
  8. 13. Mirror image of a shape
  9. 14. Branch of mathematics that studies the angles,sizes,shapes,positions,and dimensions of things
  10. 15. Four sided-polygon with all internal angles equal to 90 degrees