1. sides
CD DA
angles
∠C ∠D

2. side lengths
sides
definition (Theorem 8.7) BC

3. parallel congruent ∥ ≅
bisect
bisect

4. AD AD
Theorem 8.9
theorem 8.4 ∠D

5. H K G
125 55 J
m∠K = 125° by Theorem 8.8
Theorem 8.10

6. bisect
ST RT RT
2x x + 9 RT x 3

8. theorem 8.9
congruent
(4 - 2) 2 + (4 - 2) = 2√2
(6 - 4)2 + (0 - (-2)) = 2√2 ≅ ∥
4 - 2 1
0 - (-2)
6 - 4 1
parallel
theorem 8.9

9. 2x = 4x - 7
-2x = -7
x = 3.5
Another way to show quadrilateral KLMN is a parallelogram would be to add the diagonals to the figures and show that they bisect each other.