Across
- 1. the common intersection of the three altitudes of a triangle or their extensions
- 3. the perimeter of a circle
- 5. two adjacent angles that would add up to 180°
- 12. a rule in algebra expressed by symbols or formulae
- 13. the place within a perimeter
- 14. a straight one-dimensional figure
- 17. a plane with nine straight sides and angles
- 18. a relationship between two propositions that is true only when both propositions are simultaneously true or false
- 19. the length around an area
- 20. a number that falls in the middle of a group
Down
- 2. a quadrilateral with only parallel sides
- 4. intersecting a system of lines
- 6. an angle less than 90°
- 7. lines that are at a right angle
- 8. a line coming out of a point
- 9. the line through a vertex of a figure perpendicular to the base
- 10. the center of mass of a geometric object of uniform density
- 11. the halfway point of a line
- 15. the reverse of a statement
- 16. when the “if” and “then” statement are swapped