Theory:

A circle:
When all the points on a plane is at a fixed distance from the fixed point is called a circle.
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The line that joins the centre of the circle and any point on the circle is called the radius.
 
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A circle acts as a closure to all the points on the plane.
 
This closure can be classified into three categories:
 
1. The points that are interior to the circle.
 
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2. The points that are on the circle.
 
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3. The points that are outside the circle.
 
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Some other components of the circle:
 
A chord:
When a line segment connects any two points on the circle, then it is called a chord.
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A diameter:
The line segment that passes through the centre of the circle connecting two definite points on the circle is called a diameter.
The diameter is the longest chord on the circle.
 
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