Simple circle problem involving area and circumference

[astrololo]

What's the formula for the circumference of a circle?

c=2*$\pi$*r

 

[SteamKing]

c=2*$\pi$*r

Sigh... and what happens when you divide C by 2π ?

 

[astrololo]

Sigh... and what happens when you divide C by 2π ?

You obtian the radius. Btw why are you desesperate lol

 

[Chestermiller]

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

 

[Chestermiller]

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