Question 709347
#1, Inverse of f(r)= (pi)r^2


g(r) new function.
{{{g(f(r))=g((pi*r^2))}  and {{{g((pi*r^2))=r}}}

Also f(g(r))={{{(pi)*g(r)*g(r)=r}}}
or more simply, {{{(pi)*(g(r))^2=r}}}


That last equation can be solved for g(r),... and there be the inverse of f(r).