FP2 Edexcel

What's the hardest chapter in FP2?

complex numbers and polar coordinates

Do polar coordinates build on coordinate systems from FP1?

no relation between polars and anything at FP1

I do not even know why the chapter in FP1 is called coordinate systems.

The chapter should be called Introduction to the conic sections

I see.. Thank you!

What's the hardest chapter in FP2?

I would say the parts of the complex numbers chapter involving loci and transformations.

Polar coordinates aren't a big problem. Sketching them could be a problem, but you don't have to do that, they always give you a sketch in exam questions. This is to make it fairer for those without a graphical calculator. It does sometimes help if you understand why the equations give the graph they do.