Circle - Definition with Examples
What is a Circle?
OA = OB = OC = OD = OE = OF = OG = OH
Circles Around Us
We see circles all around us. For example, objects like buttons, bicycle tires, dart boards, clocks etc are circular in shape.
Parts of Circles
The line joining the center of the circle to the boundary is known as the radius of the circle. A circle has many radii. All radii of a circle are of equal length. In the circle above, PQ is the radius.
A line segment joining any two points on the circle is known as the chord of the circle. In the circle above, CB is the chord.
A chord that passes through the center of the circle is known as the diameter of the circle. A diameter is always the longest chord in a circle. In the figure above, AB is the diameter as it passes through the center P.
Circumference is the length of the boundary of the circle.
The circumference of a circle is about 3 times the diameter.
Relation between Radius, Diameter and Circumference
The diameter of a circle is twice its radius.
In other words, the radius of a circle is half of its diameter.
|Diameter = 2 x Radius
The circumference of a circle is approximately thrice the diameter of the circle.
|Circumference = 3 x Diameter (approximately)|
This relationship helps to solve many geometry problems.
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