from which course can i learn polar coordinates

Other than a short article in Computer Programming (https://www.khanacademy.org/computing/computer-programming/programming-natural-simulations/programming-angular-movement/a/polar-coordinates), most of the lessons on polar coordinates seem to be in Calculus or Precalculus courses.

In the Search box in the header of any Khan Academy page, search for "Polar coordinates" to find links to the individual lessons.