distance between two geo points , I am trying to convert Rhumb lines distance calculation in matlab but it is not work properly

I am trying to convert Rhumb lines distance calculation in matlab but it is not work properly can some body help :

%rhumb line
clc
th1=4.385704984670893; % latitude 1
th2=4.382316850229801; % latitude 2
lon1=  100.97986760432356  ; % longitude 1
lon2= 100.96958025244206  ; % longitude 2
Dlon=lon2-lon1;
Dth=th2-th1;
R=6371

LD=log(tan(pi/4+th2/2)/tan(pi/4+th1/2)); % latitude difference
cos(th1)
abs(LD);
q=Dth/LD;
d=sqrt((Dth)^2 + ((q)^2) * (Dlon)^2)*R
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