In a plane, suppose you have a point O called the origin, and an axis through that point – say the x-axis – called the polar axis.
Then the polar coordinates (r, θ) describe the point lying a distance of r units away from the origin, at an angle of θ to the x-axis. The value of θ may be given in degrees or radians.
Examples:


To convert from polar coordinates to Cartesian coordinates, you can use:
x = r cos θ
y = r sin θ
To convert from Cartesian coordinates to polar coordinates:
.
Since
.
So, the Cartesian ordered pair (x, y) converts to the Polar ordered pair
.