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**Day Four: The Relationship of two
circles**

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by Nami Youn

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**Objective**

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to explore the directional relationship of two circles

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**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**

**gsp file**

**Case 2 A circle is circumscribed
in another one**

**r+r' = d**

**gsp file**

**Case 3 Two circles have
two coomon points**

**r - r'< d < r + r'**

gsp file

**Case 4 A circle is inscribed
in another one**

**r - r' = d**

gsp file

**Case 5 A circle is inside
another one**

**r - r' < d**

gsp file

**Case 6 Concentric
circles**

**d = 0**

gsp file

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