Answer:
function [Area,Perimeter,L]=f_circle(x)
% Area: pi*x^2 area of circle with radius x
% Perimeter: 2*pi*x perimeter length of circle with radius x
% x can be a vector
minargs=1;maxargs=1;narginchk(minargs,maxargs); % only 1 input accepted
if ~isequal('double',class(x)) 5 input has to be type double
disp('input type not double');
return;
end
Area=pi*x.^2;
Perimeter=2*pi*x;
end