Examples of circumference in the following topics:
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- The length of the
arc around an entire circle is called the circumference of that circle.
- So the circumference of any circle is $2\pi \approx 6.28$ times
the length of the radius.
- Because the total
circumference of a circle equals $2\pi$ times the radius, a full circular rotation is $2\pi$ radians.
- In fact, radian measure is dimensionless, since it is the
quotient of a length (circumference) divided by a length (radius), and
the length units cancel.
- The circumference of a circle is a little more than 6 times the length of the radius.
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- You probably know how to find the area and the circumference of a circle, given its radius.
- The ratio of a circle's circumference to its diameter is π (pi), an irrational constant approximately equal to 3.141592654.
- The length of the circumference, C, is related to the radius, r, and diameter, d, by:
- As proved by Archimedes, the area enclosed by a circle is equal to that of a triangle whose base has the length of the circle's circumference, and whose height equals the circle's radius, which comes to π multiplied by the radius squared:
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- The circumference is the length of the path around the circle.
- The number $\pi$ is actually defined by this relationship, as the ratio of any circle's circumference to its own diameter.
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- For example, the relationship between the circumference, $C$, and diameter, $d$, of a circle is described by $\displaystyle \pi =C/d$
.
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- Ellipses are less common, mostly encountered as the orbits of planets, but you should be able to find the area of a circle or an ellipse, or the circumference of a circle, based on information given to you in a problem.