1. Chapter 8 Quadrilaterals

2. Section 8-1 Quadrilaterals

3. Quadrilateral A closed geometric figure with four sides and four vertices.

4. Any two sides, vertices, or angles of a quadrilateral are either consecutive or nonconsecutive.

5. Diagonals Segments whose endpoints are nonconsecutive vertices of a quadrilateral

6. Theorem 8-1 The sum of the measures of the angles of a quadrilateral is 360°.

7. Section 8-2 Parallelograms

8. Parallelogram A quadrilateral with two pairs of parallel sides

9. Theorem 8-2 Opposite angles of a parallelogram are congruent.

10. Theorem 8-3 Opposite sides of a parallelogram are congruent.

11. Theorem 8-4 The consecutive angles of a parallelogram are supplementary.

12. Theorem 8-5 The diagonals of a parallelogram bisect each other.

13. Theorem 8-6 The diagonal of a parallelogram separates it into two congruent triangles.

14. Section 8-3 Tests for Parallelograms

15. Theorem 8-7 If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram.

16. Theorem 8-8 If one pair of opposite sides of a quadrilateral is parallel and congruent, then the quadrilateral is a parallelogram.

17. Theorem 8-9 If the diagonals of a quadrilateral bisect each other, then the quadrilateral is a parallelogram.

18. Section 8-4 Rectangles, Rhombi, & Squares

19. Rectangle A parallelogram with 4 right angles

20. Rhombus A parallelogram with 4 congruent sides

21. Square A parallelogram with 4 congruent sides and 4 right angles

22. Theorem 8-10 The diagonals of a rectangle are congruent

23. Theorem 8-11 The diagonals of a rhombus are perpendicular

24. Theorem 8-12 Each diagonal of a rhombus bisects a pair of opposite angles

25. Section 8-5 Trapezoids

26. Trapezoid A quadrilateral with one pair of parallel sides

27. Bases and Legs The parallel sides are called bases The nonparallel sides are called legs

28. Base Angles Each trapezoid has two pairs of base angles

29. Median The segment that joins the midpoints of its legs

30. Theorem 8-13 The median of a trapezoid is parallel to the bases, and the length of the median equals one-half the sum of the lengths of the bases.

31. Theorem 8-14 Each pair of base angles in an isosceles trapezoid is congruent.