CK12 - Geometry

5. Definitionof parallelogram


6. 
   


7. 
   
   
   
   6. AlternateInteriorAnglesTheorem
   
   
   
   


8. 
   
   
   
   7. Reflexiveproperty
   
   
   
   


9. ASA TriangleCongruencePostulate


10. 
    


11. Definitionof congruenttriangles(all corre-
    spondingsidesand anglesof congruenttrian-

9.

gles are congruent)

10. 
    
    
    
    10. Angleadditionpostulate
    
    
    
    


11. 
    
    
    
    11. Angleadditionpostulate
    
    
    
    


12. 
    
    
    
    12. Substitution
    
    
    
    

Now we haveshownthat oppositeanglesof a parallelogramare congruent[Diff: 3].

9. [Diff: 3]


10. See below. The red line is a line of reflection.Giventhis symmetry, we can concludethat
    [Diff: 3].

UsingParallelograms

LearningObjectives

• Describethe relationshipsbetweenoppositesidesin a parallelogram.


• Describethe relationshipbetweenoppositeanglesin a parallelogram.


• Describethe relationshipbetweenconsecutiveanglesin a parallelogram.