So I think you're looking for something like this
function [k] = myawesomefunction(x1,x2,x3,y1,y2,y3)
%MYAWESOMEFUNCTION with 6 input arguments x1, x2, x3, y1, y2, y3 and 1
%output argument k
a = sqrt((x1-x2)^2+(y1-y2)^2); b = sqrt((x2-x3)^2+(y2-y3)^2); c = sqrt((x1-x3)^2+(y1-y3)^2);
s=(a+b+c)/2;
k=sqrt(s.*(s-a).*(s-b).*(s-c));
end
If you also want the other variables a, b, c and s, you can just change it to this
function [a, b, c, s, k] = myawesomefunction(x1,x2,x3,y1,y2,y3)
You need to save the file with the same name as you gave the function, so in this case save it as 'myawesomefunction.m'
You can call your function in your main file like so:
myoutputK = myawesomefunction(12,23,45,56,78,91); %if you only have 1 output argument
[outputA,outputB,outputC,ouputS,outputK] = myawesomefunction(12,23,45,56,78,91); %if you have more than 1 output
