function [ y ] = expfroot (x,k)
%y=expfroot(x)
%y=expfroot(x,k)
%
%functional root of power k of exponent.
%if k is not specified, k is assumed to be 2

if nargin==1
  K=0.5;
else
  K=k;
end

y=etetr(etetri(x)+K);

return
