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Across 1. a quadrilateral whose opposite sides are parallel 4. lines in the same plane that never meet 6. angles formed by parallel lines and a transversal 7. a figure with sides of unequal lengths 8. a geometric figure with four sides 10. a quadrilateral with exactly one pair of parallel sides 13. a line that crosses parallel lines 15. a proof that shows that shows that conclusion can not be false because accepted facts would be contradicted 17. lines in space that are not coplanar and never meet 18. A closed figure that has 3 or more line segments on the same plane

Down 2. angles formed by parallel lines cut by a transversal 3. a figure with two sides of equal length 5. lines in the plane 9. a parallelogram with four right angles 11. a parallelogram with four equal sides 12. a rectangle with sides of equal length 14. angles formed by intersecting lines 16. angles formed by lines that cross each other at 90 degrees