Today we use cartesian coordinates extensively which are named after the former. The relationship between two sets of numbers are often represented via a graph or an equation. Such relationships, if plotted on a coordinate system are lines and hence termed linear . The cartesian coordinate system is such a cartesian product of two number lines, labeled x and y . These coordinates are called ordered pairs and are separated by commas and enclosed within parentheses.
Lattice points are points in the xy -plane with integer coordinates for both x and y .
A relation is a set of ordered pairs. A function is a relation for which there is exactly one value of the dependent variable for each value of the independent variable. This does not mean to multiply f by x . It means f is the name of the function with x as the independent variable. The set of values of the independent variable is the domain .