Question 824972
{{{ A = pi*((R - r)/2)^(2) }}}
Divide both sides by {{{ pi }}}
{{{ A/pi = ((R - r)/2)^(2) }}}
Take the square root of both sides
{{{ sqrt( A/pi ) = ( R-r )/2 }}}
Multiply both sides by {{{ 2 }}}
{{{ 2*sqrt( A/pi ) = R-r }}}
Add {{{ r }}} to both sides
{{{ 2*sqrt( A/pi ) + r = R }}}