Find the dimensions of the rectangle

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SUMMARY

The discussion focuses on finding the dimensions of the rectangle with the largest area that can be inscribed in a circle of radius r. The key equations involved are the circle equation, (x-a)² + (y-b)² = r², and the area formula, A = 4xy. Participants express confusion regarding the differentiation process required to maximize the area and the proper setup of the equations. The conversation highlights the necessity of using the product rule effectively in calculus to derive the correct dimensions.

PREREQUISITES
  • Understanding of calculus, specifically differentiation and the product rule
  • Familiarity with the equation of a circle
  • Knowledge of maximizing functions and area calculations
  • Basic algebra skills for manipulating equations
NEXT STEPS
  • Study the application of the product rule in calculus
  • Learn about optimization techniques in calculus
  • Review the derivation of area formulas for geometric shapes
  • Explore the relationship between inscribed shapes and their circumscribing circles
USEFUL FOR

Students studying calculus, particularly those focusing on optimization problems, as well as educators looking for examples of geometric applications in calculus.

UWMpanther
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Homework Statement


Find the dimensions of the rectangle of largest area that can be inscribed in a circle of radius r.


Homework Equations



(x-a)^2 + (y-b)^2 = r^2
max area = 2x(2y)
= 4xy

The Attempt at a Solution



(x-a)^2 + (y-b)^2 = r^2
= y=r-(x-a)+b

I then plug this into the max area
= 4x(r-(x-a)+b)

I know I need to differentiate, but I'm not sure how to go about this. I know I need to use the product rule, if its setup properly.
 
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UWMpanther said:

Homework Statement


Find the dimensions of the rectangle of largest area that can be inscribed in a circle of radius r.


Homework Equations



(x-a)^2 + (y-b)^2 = r^2
max area = 2x(2y)
= 4xy

The Attempt at a Solution



(x-a)^2 + (y-b)^2 = r^2
= y=r-(x-a)+b
How in the world did you get this? Surely not by taking the square root of both sides!

I then plug this into the max area
= 4x(r-(x-a)+b)

I know I need to differentiate, but I'm not sure how to go about this. I know I need to use the product rule, if its setup properly.
No, it not at all set up properly!
 


Ok wow I can't believe I did that.

So I FOIL it out and get this

x^2 = r^2 + 2ax - a^2 - y^2 + 2by - b^2

x= r-a-b+sqrt(2ax)+sqrt(2by)

Does this look better?
 

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