The Euclidean plane parametrized by coordinates, so that each point is located based on its position with respect to two perpendicular
lines, called coordinate axes. They are two copies of the real
line, and the zero point lies at their intersection, called the origin.
The coordinate axes are usually called the x-axis
and y-axis, depicted above. Point 
is associated with the coordinates 
corresponding to its orthogonal projections onto the 
-axis and the 
-axis respectively.
