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A circle with radius 4 is translated 2 units. What is the area of the region swept out by the circle?

 
 Dec 31, 2024
 #1
avatar+518 
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The area swept out by the circle is 6 pi + 20.

 Dec 31, 2024
 #2
avatar+130042 
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Translate the top circle  with the equation  x^2 + (y-2)^2  = 16   to the bottom circle

 with the equation x^2 + y^2 = 16

 

Let Area A be the area of rhombus ACBD =  4^2 * sin (151.04°) ≈ 7.75

 

Let Area A  + Area B  = the area of the portion of the bottom circle bounded by minor arc  CED  = 

pi * 4^2 * (151.04 / 360) ≈ 21.09

 

Area B  = Area A + Area B - Area A  21.09 - 7.75 ≈ 13.35

 

Let Area B + Area C  = the area of the portion of the top circle bounded by major arc CFD = 

pi * 4^2 * ( 360 -151.04) / 360 ≈ 29.18

 

The area swept out by the translation of the top circle to the bottom circle  = 

Area  B + Area  C - Area B  =   Area C   = 29.18 - 13.35  ≈ 15.84

 

cool cool cool

 Jan 1, 2025
edited by CPhill  Jan 2, 2025
edited by CPhill  Jan 3, 2025

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