Problem of Symbolic function evaluation

syms u [2 1]

f(u) = u'*u;

f(1,2) % Correct syntax the ans is 5

f([1;2]) %Incorrect syntax Symbolic function expected 2 input arguments but received 1.

Why can the input of a function only be two variables, not a vector? What if there are many variables, such as 100 variables? It is too troublesome to input 100 values one by one during evaluation.

Answer 1

[Torsten]

u = sym('u',[2 1]);
f = u.'*u

f = 

result = subs(f,u,[1;2])

result = 

5

[Morty]

Thank you very much for your answer! I have been confused about this problem for some days.