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```
Date: 10/07/98 at 21:16:44
From: Jason

Why is a circle divided into approximately 6.28 radians?
```

```
Date: 10/08/98 at 13:18:41
From: Doctor Peterson

Hi, Jason,

A complete circle, 360 degrees, is exactly 2 pi radians. Do you
recognize that from the formula for the circumference of a circle,
2 pi r? That's because the number of radians in an angle is defined as
the length of  the arc of a unit circle subtended by the angle:

***********
******           ****/*
***                    /  ***
***                      /      ***
*                        /          *  L
**                        /            **
*                         /               *
*                         /                 *
*                         /                   *
*                         /                     *
*                        / A                    *
*                       *------------------------
*                                   1           *
*                                               *
*                                             *
*                                           *
*                                         *
**                                     **
*                                   *
***                             ***
***                       ***
******           ******
***********

The radian measure of the angle A is defined as the length of the arc
L. You can think of radians as just using a flexible tape measure to
measure around the circle - the most natural way to measure an angle.

So if A is the whole circle, its measure is the whole circumference,
or 2 times pi, which is about 6.28.

- Doctor Peterson, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
High School Conic Sections/Circles
High School Geometry
Middle School Conic Sections/Circles
Middle School Geometry
Middle School Terms/Units of Measurement

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