% F = Four(f,x,xi) computes the Fourier transform using the definition
%      F(xi) = int(f(x)*exp(-2*pi*i*xi*x),x,-inf,inf)
% 
% x and xi must be declared as symbolic variables, e.g., using
%      syms x xi
function F = Four(f,x,xi)
F = subs(fourier(f,x,xi),xi,2*pi*xi);
