1. Proving that a quadrilateral is a Parallelogram
Geometry
Regular Program SY
Source:
Discovering Geometry (2008) by Michael Serra
Geometry (2007) by Ron Larson

2. Proving Parallelograms
When is a quadrilateral a parallelogram?
If both pairs of opposite sides are parallel
If both pairs of opposite sides are congruent
If both pairs of opposite angles are congruent
If the diagonals bisect each other
If a pair of opposite sides are both congruent and parallel

3. Exercises
Is the quadrilateral a parallelogram or not ? Why?
YES! 

4. Exercises
Is the quadrilateral a parallelogram or not ? Why?
YES! 

5. Exercises
Is the quadrilateral a parallelogram or not ? Why?
YES! 

6. Exercises
Is the quadrilateral a parallelogram or not ? Why?
No 

7. Exercises
Is the quadrilateral a parallelogram or not ? Why?
No 

8. Exercises
Is the quadrilateral a parallelogram or not ? Why?
No 

9. Exercises
Is the quadrilateral a parallelogram or not ? Why?
No 

10. Exercises
Is the quadrilateral a parallelogram or not ? Why?
YES! 

11. Exercises
Is the quadrilateral a parallelogram or not ? Why?
YES! 

12. What must be the values of x and y to make ABCD a parallelogram?
Exercises
What must be the values of x and y to make ABCD a parallelogram?

13. What must be the values of x and y to make ABCD a parallelogram?
Exercises
What must be the values of x and y to make ABCD a parallelogram?

14. What must be the values of x to make ABCD a parallelogram?
Exercises
What must be the values of x to make ABCD a parallelogram?