function [dydt] = prob_7_4_fn(t,y)
% 
% Written by:
% -- 
% John L. Weatherwax                2006-05-21
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

dydt = (2/sqrt(pi))*exp(-t^2);