Circular crown area


THE circular crown is a region of the plane formed from two circlesfrom the same center but different radii, one larger and one smaller.

In the figure below, a circle of radius r is inscribed in a circle of radius R, where R > r. Note that the center of the two circles is the same.

circular crown

The circular crown is the colored region in the figure and corresponds to the difference between the larger circle and the smaller circle.

An example of an everyday circular crown is the rim of a circular wall clock.

Clock

circular crown area

THE circular crown area it can be obtained from the difference between the area of ​​the larger circle, of radius R, and the area of ​​the smaller circle, of radius r.

How to calculate the circle area?

\dpi{120} \mathrm{A_{Circle\, largest} = \pi R^2}
\dpi{120} \mathrm{A_{Circle\, smaller} = \pi r^2}

The difference between these areas is:

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\dpi{120} \mathrm{A_{Circle\, larger} - A_{Circle\, smaller} = \pi R^2 - \pi r^2 = \pi (R^2-r^2) }

Therefore, the circular crown area formula é:

\dpi{120} \mathbf{A_{Crown \, circular} = \boldsymbol{\pi}(R^2-r^2) }

On what:

  • \dpi{120} \boldsymbol{\pi\approx 3.14}
  • R: radius of the largest circle;
  • r: radius of the smallest circle.

Example:

Calculate the area of ​​a circular crown delimited by two circles of radius 5 and 3 meters.

We have R = 5 and r = 3. Let's apply in the formula:

\dpi{120} \mathrm{A_{Crown \, circular} = 3.14\cdot (5^2-3^2) =50.24}

Therefore, the area of ​​this circular crown is equal to 50.24 m².

You may also be interested:

  • circumference length
  • elements of the circle
  • Arcs and circular motion
  • Difference between circumference, circle and sphere

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