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The coordinate systems most commonly used in engineering analysis are the Cartesian, cylindrical, and spherical systems. These systems are illustrated in Figures $$\PageIndex{1}$$, $$\PageIndex{2}$$, and $$\PageIndex{3}$$, respectively. Note that the use of variables is not universal; in particular, it is common to encounter the use of $$r$$ in lieu of $$\rho$$ for the radial coordinate in the cylindrical system, and the use of $$R$$ in lieu of $$r$$ for the radial coordinate in the spherical system.
Figure $$\PageIndex{1}$$: Cartesian coordinate system ( CC BY SA 4.0; K. Kikkeri) Figure $$\PageIndex{2}$$: Cylindrical coordinate system. ( CC BY SA 4.0; K. Kikkeri) Figure $$\PageIndex{3}$$: Spherical coordinate system. ( CC BY SA 4.0; K. Kikkeri)