When the functions f1 and F2 are in the path where function f3 can acess, then you can directly use the functions name to access the function.
function out = f3(in1,in2) a = f1(in1); % call th function signature end As shown above the usage with f1, even F2 can be called within the function f3.
The scope variables within a function are only present till the execution is within the function. Thus, you cannot acces intermediate variables of f1 and f2 in f3. In case it is required to use them, pass them as outputs to the respective functions.
For more details about functions, look at topics in the page here .
Hope this helps. Regards, Sriram