Day Four: The Relationship of two circles

by Nami Youn


Objective

to explore the directional relationship of two circles


1. Direction of two circles

Let O & O' be the center and  r & r' be the radius of given circles, respectively.  r > r'.
Let d be the distance between the centers of two circles.



Case 1  A circle is outside another one


 
 

r+r' <  d

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Case 2  A circle is circumscribed in another one


 
 


 
 

r+r' =  d





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Case 3  Two circles have two coomon points

 
 


 

r - r'< d < r + r'





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Case 4  A circle is inscribed in another one

 
 



 
 
 
 

r - r' = d




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Case 5  A circle is inside another one

 
 


 
 
 
 

r - r' < d





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Case 6  Concentric circles

 
 

d = 0






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