Simple circle problem involving area and circumference

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Homework Help Overview

The problem involves a stone thrown into still water, creating ripples that form circles. The circumference of the circle is given as 10 ft, increasing at a rate of 3 ft per second, and the task is to determine how fast the area of the circle is increasing without using differentiation, but rather a limiting process.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss expressing the area as a function of circumference and question the necessity of using limits instead of differentiation. There are attempts to clarify the relationship between area and circumference using algebra.

Discussion Status

The discussion is ongoing with various interpretations being explored. Some participants are attempting to derive expressions for area in terms of circumference, while others emphasize the need to adhere to the limiting process as specified in the problem statement. There is no explicit consensus on the approach to take.

Contextual Notes

Participants note that the problem constraints include a requirement to avoid differentiation, leading to confusion about the methods available for solving the problem. The original poster expresses uncertainty about how to proceed under these constraints.

  • #31
SteamKing said:
What's the formula for the circumference of a circle?
c=2*##\pi##*r
 
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  • #32
astrololo said:
c=2*##\pi##*r
Sigh... and what happens when you divide C by 2π ?
 
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  • #33
SteamKing said:
Sigh... and what happens when you divide C by 2π ?
You obtian the radius. Btw why are you desesperate lol
 
  • #34
I was hoping you would start working this problem using the method I was leading you to in post #25. This method involves using limits (which is the main requirement for your teacher). If you do what I suggested in post #25 (which is the first step in the derivation), I can lead you through, step by step, to the final result. But I need you to start.

Chet
 
  • #35
$$A(t)=\frac{C^2(t)}{4\pi}$$
$$A(t+Δt)=\frac{C^2(t+Δt)}{4\pi}$$
$$A(t+Δt)-A(t)=\frac{C^2(t+Δt)-C^2(t)}{4\pi}$$
Do you know how to factor the numerator of the right hand side?
 

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