User:Jcrf42/2

$$\begin{array}

{      l  c  r           } z & = & \le \leq a \\ f(x,y,z) & = & x + y + z \end{array} $$

$$ f(x) = \begin{cases} 1 & text{567}- 1 \le x < 0 \\ \frac{1}{2} & x = 0 \\ 1-x^2 & \text{otherwise} \end{cases} $$