What are polar coordinates used mostly for?

Thank you for the invitation, but not the field of specialization

Polar Coordinates is used where angle need to be specified. Few cases, length & Angle may be known and in those cases use polar.

Cartesian Coordinate system is much easier. Decision is made based on situation.

I would like to add the following utility

Graphing polar functions 

lines , points , rectangles

Polar coordinates are used to drawing lines,rectangles,points etc.

Polar coordinates are used to draw shapes, lines, setting limits.... starting with0,0 as the starting point (X,Y) ... so1,5 is1 in direction of x and5 points to y with your starting point at0,0 (1 to the right and5 up);

-x,-y is x to the left and y is down

polar coordinates are used ( lines , sitting limits ) starting  0,0  starting point ( X, Y)  and used

where angle to be specified.  

Correct use of Polar Coordinates is to Draw the Angular lines. you can on and off the polar coordinate by pressing F10 key and also add the additional angles by clickin new in Polar drafting setting dialog Box.

you may make many more thing i.e. copy the objects, points or some elements with specific angles.

They use to drawing lines , points , rectangles  ,  etc .and/or copying any of elements in the circular spaces ,sectors , extends  .