Graph of a function of two variables

Summary

• If \(f:A→B\) is a function of two variables, then the set \((x,y,f(x,y)):(x,y)∈A\) is called the graph of \(f\) (3-dimensional).
• If \(f:A→B\) is a function of two variables, then the set \({(x,y):(x,y)∈A,f(x,y)=c}\) is called a level set or a level curve of \(f\) or a graph of the equation \(f(x,y)=c\) (2-dimensional).