I am deriving an equation modelling a magnetic guitar pickup and I am stuck.
I am trying to derive based on a paper for guitar pickups and it uses a magnetic masses method to find the magnetic flux at point c from magnetic field generated by point a and steel point b. I am confused where the integral comes from:
These papers uses the same method https://www.dafx17.eca.ed.ac.uk/papers/DAFx17_paper_79.pdf https://scholarship.rollins.edu/cgi/viewcontent.cgi?article=1014&context=stud_fac
EDIT: Apologies to clarify my question more I am trying to understand where this three point integral comes from in this section of the papers shown above.