crossword puzzle #3

12345678910111213141516171819
Across
  1. 1. a four sided shape
  2. 10. a plane figure with four straight sides and four right angles
  3. 11. is a triangle with one obtuse angle
  4. 12. a quadrilateral with only one pair of parallel sides
  5. 15. the number of different digits a system of counting uses to represent numbers
  6. 16. a triangle that all sides are different lengths
  7. 18. a triangle that has two sides of equal length
  8. 19. having an outline or surface that curves inward
Down
  1. 2. formed by all angles measuring less than 90˚
  2. 3. a plane with at least three straight sides/angles
  3. 4. a four-sided plane figure with opposite sides parallel
  4. 5. with opposite equal acute angles
  5. 6. having only interior angles measuring less than 180°
  6. 7. the angles opposite the congruent sides are congruent
  7. 8. two pairs of consecutive, congruent sides
  8. 9. the distance around a the edge of a shape
  9. 13. lie on a line joining two opposite corners
  10. 14. triangle in which one of the angles is a 90∘ angle
  11. 17. all three sides are equal lengths