fillbetween - How do I use a drawn arc as border? - TeX

The question is writen in the title, i got the grey filled part and it has to fit on the arc. I did it manualy but supose there is a better solution i can't figure out. Thank you in advance, Leo.\documentclass[tikz,border=10pt]{standalone}\usetikzlibrary{3D, calc, matrix}\usepackage{tikz}\usepackage{mathcomp}\usepackage{amsmath}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{caption}\begin{document} \begin{figure} \centering \begin{tikzpicture} %3D-Koordinatensystem: \draw[->, >=latex] (-5,0,0) -- (5,0,...Read more