# Functions of two variables

Summary

- If \(f:A→B\) where \(A⊆R^2\) , \(B⊆R\) then we say that \(f\) is a real-valued function of two real variables , \(z=f(x,y)\) .
- If the domain is not specified, it is given by the natural domain , which is the subset of \(R^2\) for which the formula given for \(f\) is valid.