Polar coordinate System and converting equations from polar to rectangular and viceversa

Polar coordinate system is a plane with Pole(point O) and polar axis  which is horizontal axis from point O. Any point P in this plane is assigned polar coordinates represented as P(r, theta)

we measure theta as positive when moving counterclockwise and negative when moving clockwise.

If r > 0, then P is on the terminal side of  theta . If r < 0, then P is on the terminal side of   (theta + pi).