Can you post the code to trapezes - the error message says the problem is in there, you have something like;
function Itr=trapezes(n)
if n<1
Itr = 5;
end
end
The problem here is that if n > 1, there is no case that assigns Itr, so there is no output variable. You could use;
function Itr=trapezes(n)
Itr=0;
if n<1
Itr = 5;
else
Itr = 1;
end
end
Now you have a success case, a fail case, and a default case that you can check against.
