Three mutually tangent circles

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SUMMARY

The problem involves calculating the radius r of three mutually tangent circles that enclose a shaded area of 24 square units. The central angle for each sector formed by the circles is 60 degrees, as the centers of the circles form an equilateral triangle. The area of a sector is calculated using the formula A = (central angle * π * r²) / 360. By relating the area of the shaded region to the sectors and the triangle, the value of r can be determined as r = sqrt(360 * area of sector / (60 * π)).

PREREQUISITES
  • Understanding of geometry, specifically properties of equilateral triangles.
  • Knowledge of circle geometry, including sector area calculations.
  • Familiarity with the formula for area of a sector: A = (θ * π * r²) / 360.
  • Basic algebra for solving equations involving variables.
NEXT STEPS
  • Learn how to derive the area of an equilateral triangle given the side length.
  • Study the relationship between the radius of a circle and the area of its sector.
  • Explore the concept of tangent circles and their geometric properties.
  • Practice solving problems involving multiple geometric shapes and their areas.
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Students studying geometry, mathematics educators, and anyone interested in solving complex geometric problems involving circles and triangles.

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Homework Statement



Three mutually tangent circles with the same radius r enclose a shaded area of 24 square units. Determine the value of r to the nearest unit.

Homework Equations


do i use the arc length formula to find the answer?


3. The Attempt at a Solution

A=(central angle*pi*r^2)/360
the central angle is 60 because if u draw a triangle between the three centers of the circles it is equilateral...but i don't know how to get r with only this information
 
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Hi Megrs@! :smile:

(have a pi: π and a degree: ° and try using the X2 tag just above the Reply box :wink:)
Megrs said:
Three mutually tangent circles with the same radius r enclose a shaded area of 24 square units. Determine the value of r to the nearest unit.

the central angle is 60 because if u draw a triangle between the three centers of the circles it is equilateral...but i don't know how to get r with only this information

You're almost there!

Stay with that triangle …

it has the shaded area inside it, so what's left? :wink:
 
tiny-tim said:
Hi Megrs@! :smile:

(have a pi: π and a degree: ° and try using the X2 tag just above the Reply box :wink:)


You're almost there!

Stay with that triangle …

it has the shaded area inside it, so what's left? :wink:


what is left are the sectors of the circles and if u make each one=x then 3x+24=A of the triangle. the arc length is r(2*pi*central angle/360) i don't think that gives any useful information though...except maybe help prove the answer once i find it...
 
Hi Megrs! :wink:

(what happened to that π i gave you? :confused:)

Yes, three sectors …

now, you know the radius and the angle of each sector, so the area is … ? :smile:
 
tiny-tim said:
Hi Megrs! :wink:

(what happened to that π i gave you? :confused:)

Yes, three sectors …

now, you know the radius and the angle of each sector, so the area is … ? :smile:


what n?? i don't get it...
no, i know the angle of the sectors...i do NOT know the radius that is what i have to find...so i don't know the area of the sectors either
 
(it's not an "n", its a "π" !)

Yes, but you know that r is half the side of your equilateral triangle! :wink:

so the area of the shaded part (as a multiple of r) is … ? :smile:
 
i know r is half the side i don't get how to relate this all together because the shaded part is not part of the circles...the area of the shaded part is 24. the area of a sector is (24-area of the triangle)/3...
 
so as a factor of r, the area of a sector is … ? :smile:
 
tiny-tim said:
so as a factor of r, the area of a sector is … ? :smile:

area of a sector is 60*r^2*pi/360
 
  • #10
Megrs said:
area of a sector is 60*r^2*pi/360

so as a multiple of r, the area of the shaded part is … ? :smile:
 
  • #11
i don't know because the shaded part is not part of the sectors...
r=sqrt(360*area of sector/60pi)
?
 

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