We have usually used cartesian co-ordinates(x,y).Polar coordinates are an alternative system which can describe position of a point.In polar co-ordinates any point can be described in terms of its distance and direction from a fixed point O.

Each point P in the plane is assigned polar coordinationates according to the following rules:
     r is the directed distance from O to P.
     θ is the directed angle between the polar axis (usually a ray from point O to the east) to the line OP.