Geometry

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Across
  1. 3. a parallelogram with all of its sides the same length
  2. 9. a triangle having three acute angles
  3. 11. two nonintersecting lines which do not belong to a common plane
  4. 12. a convex polygon that is both equilateral and equiangular
  5. 13. a curve that ends at the same point it began
  6. 14. two nonintersecting lines belonging to a common plane
  7. 16. a rectangle with all sides of equal length
  8. 17. two angles whose sum of their measures is 180 degrees
  9. 19. a quadrilateral with exactly one pair of parallel sides
  10. 20. a simple closed polygonal curve
Down
  1. 1. an angle greater than 90 degrees but less than 180 degrees
  2. 2. an angle of measure 180 degrees
  3. 4. two angles that have a common side and nonoverlapping interiors
  4. 5. two angles whose sum of their measures is 90 degrees
  5. 6. angles measuring between 0 and 90 degrees
  6. 7. a pair of nonadjacent angles formed by two intersecting lines
  7. 8. a figure that contains the segment for each pair of point P and Q contained in the figure
  8. 10. a triangle having at least two sides of the same length
  9. 15. a simple closed surface formed from planar polygonal regions
  10. 18. a curve that never touches a point more than once