Polar coordinates
The Cartesian system of coordinates, or rectangular coordinate, is the most widely known because it's the most common. We subdivide the plane with columns and rows and each position is located by knowing the column and row. At school most people should have had a teacher who compared the Cartesian system with the game Battleship or a chessboard.
There is another system of coordinates called Polar coordinates that locates points with two coordinates: angle and distance.
In the Cartesian system a function cannot be a circle. In the polar system it can be a circle. The Cartesian system is easier to understand because in it we have left and right, up and down, exactly as in daily life. However, the polar system has angle and distance. Every point in it has its own unique angle and distance.
