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Radian facts for kids

Kids Encyclopedia Facts
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Definition of a radian
Circle radians
A radian is a unit of angular measure. A revolution of a circle has an angle of 2π radians.

A radian is a special way to measure angles. Think of it like another way to measure how wide an angle is, just like you use degrees. You'll often see it written with the symbol "rad" or sometimes a small "c" (like c) which stands for "circular measure." Radians are super important in math and science, especially when dealing with circles.

Why We Use Radians

Most people who study math or physics use radians instead of degrees. This is because some math problems, especially in trigonometry (which studies triangles and angles) and calculus (which studies change), become much simpler when you use radians.

For example, when talking about how fast something spins, like a wheel, scientists use "radians per second." This is a common way to measure angular velocity (how quickly an angle changes).

Also, people who use a telescope or a sniper scope often use "milliradians." This helps them describe distances they see through the scope very precisely.

Changing Between Radians and Degrees

It's easy to switch between radians and degrees. Here's what you need to know:

  • 1 radian is about 57.3 degrees.
  • A full circle has 2π radians. This is about 6.28 radians.
  • Remember, π (pronounced "pie") is a special number in math, roughly 3.14159.

Here are the formulas to change between them:

  • To go from radians to degrees:

 :2\pi\mbox{ rad} = 360^\circ  :1 \mbox{ rad} = \frac {360^\circ} {2 \pi} = \frac {180^\circ} {\pi} \approx 57.29577951^\circ So, if you have x radians, you can find the degrees by doing:  :x \mbox{ rad} = \left(\frac{180x}{\pi}\right)^\circ.

  • To go from degrees to radians:

 :360^\circ=2\pi\mbox{ rad}  :1^\circ=\frac{2\pi}{360}\mbox{ rad}=\frac{\pi}{180}\mbox{ rad} \approx 0.01745329\mbox{ rad}

Learn More

  • Steradian: This is like a radian, but for measuring angles in 3D space (like the angle of a cone).
  • Tau: Another mathematical constant that represents a full circle in radians (2π).

See also

Kids robot.svg In Spanish: Radián para niños

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