Question 11821
{{{C= 2*pi*r}}}  and {{{A= pi*r^2}}}


You want a formula for the Area in terms of the Circumference C.


So, solve for r in the first equation, by dividing both sides by {{{2*pi}}}.

{{{C/(2*pi) = (2*pi* r)/(2*pi)}}}

{{{r= C/(2*pi)}}}


Substitute this into the second formula, and you will have:

{{{A = pi * r^2}}}
{{{A = pi * (C/(2*pi))^2}}}
{{{A = pi * (C^2)/ (4*pi^2)}}}


Divide out the {{{pi}}} factor 

{{{A = (C^2) /(4*pi) }}}


I suppose without any equal signs the final answer is this: {{{(C^2)/(4*pi)}}}


R^2 at SCC