Minimum value function It's just a very simple question, is there a function defined and that tells you the minumum and maximum value of a list of variables, like:
min(4, 3) = 3
min(2, 19) = 2
max(1, 10, 3) = 10
Is that the way to write it? or is there a accepted way of doing it?
I'm just a high-schooler and I like playing with math sometimes and I wanted to know if there's a more formal way of writing min() and max(), so don't get mad if it's a very obvious thing to you. Thanks. 
 A: There are two ways to answer this question:

Answer 1: (This was given by Nitin in the comments)
We can write
$$\min(a,b) = \frac{a+b - |b-a|}{2}$$
and
$$\max(a,b) = \frac{a+b + |b-a|}{2}$$
To where this first expression comes from, observe that if $b \ge a$, then $|b-a| = b-a$, so $\frac{a+b - |b-a|}{2} = \frac{a+b - (b-a)}{2} = a$, and if $b < a$, then $|b-a| = a-b$, so $\frac{a+b - |b-a|}{2} = \frac{a+b + (b-a)}{2} = b$.  To get the second expression, notice that $\min(a,b) + \max(a,b) = a+b$, then rearrange and solve for $\max(a,b)$.  If we want to take the maximum over larger (finite) sets of real numbers, we can use the identities
$$\min(a_1, a_2, \cdots a_n) = \min(\min(a_1, a_2, \cdots, a_{n-1}), a_n)$$
$$\max(a_1, a_2, \cdots a_n) = \max(\max(a_1, a_2, \cdots, a_{n-1}), a_n)$$

Answer 2:
The expressions $\min$ and $\max$ are already well defined functions.  Many people get the idea in high school that a function is something that you can write out a 'rule' or 'formula' for, but this isn't correct.  The definition of a function is an object which takes an input and returns an output (this can be made precise using set-theoretic ideas).  The functions $\min$ and $\max$ take as input pairs of (real) numbers (or, if you like, nonempty sets of real numbers), and return the smallest/largest number in the pair (set), respectively.
