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Radius facts for kids

Kids Encyclopedia Facts
Radius
The radius of a circle

In geometry, the radius of a circle or sphere, written as r, is the shortest connection between the center and the boundary. It is either the distance from the center to the perimeter (in the case of a circle), or the distance from the center to the surface (in the case of a sphere). It is half of the diameter. That is, when r is the radius and d is the diameter:

r = d ÷ 2

d = 2 x r = r + r

The relationship between the radius {\displaystyle r} and the circumference {\displaystyle c} of a circle is ~c = 2\pi r.

The area {\displaystyle A} of a circle of radius {\displaystyle r} is {\displaystyle ~A = \pi r^2.}

Related pages

Images for kids

  • Regular polygon radius square

    A square, for example (n=4)

See also

Kids robot.svg In Spanish: Radio (geometría) para niños

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Radius Facts for Kids. Kiddle Encyclopedia.