Geometry

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Across
  1. 3. (draw pic)rectangle
  2. 4. A shape with 10 sides
  3. 9. a2+b2=c2
  4. 11. (Draw pic)consecutive angles
  5. 13. if not A then not B
  6. 14. The point where all 3 altitudeds of the triangle intersect
  7. 15. A line that intersects 2 or more coplanar lines at differnt points
  8. 17. An unproven statement based on observations
  9. 18. the number of unit squares that cover the surface of a closed figure
Down
  1. 1. (Draw pic)angle-bisector
  2. 2. Three or more points that lie on the same plane
  3. 5. (draw pic)colinear points
  4. 6. The equidistant from both endpoints
  5. 7. (draw pic)acute angles
  6. 8. The length of the outline of a shape
  7. 10. (draw pic)centroid
  8. 12. A specific case where the conjecture is wrong
  9. 16. (draw pic)angle