# Unit vectors in different coordinates

by JasonHathaway
Tags: coordinates, unit, vectors
 P: 77 Hi everyone, I've some points I want to make sure of. 1- When converting a "POINT" from a coordinate system to another, I'll just use the derived equation to convert (e.g. (1,2,3) from cartestian to cylindrical: $\rho=\sqrt{x^{2}+y^{2}}, \phi=tan^{-1}\frac{y}{x}, z=z$ 2- When converting an "EQUATION" (e.g. $\sqrt{x^{2}+y^{2}}=\frac{x^{2}y}{y^{2}x}$), I'll use the same approach as 1. 3- When converting a "VECTOR" (e.g. $4\vec{i}+3\vec{j}+6\vec{k}$), I must convert the unit vector $\vec{i}, \vec{j},\vec{k}$ into their equivalent in my desired coordinate system, whether that vector is A unit vector or not, and I cannot put in the form of a point (e.g. (4,3,6) ) and use the same approach as 1. Okay, and for 3: a) To convert from cartesian to cylindrical: Since $x=\rho cos(\phi), y=\rho sin(\phi), z=z$, then: $\frac{dx}{d \rho}=cos(\phi),\frac{dx}{d \phi}=-\rho sin(\phi), \frac{dx}{dz}=0$ $\frac{dy}{d \rho}=sin(\phi),\frac{dy}{d \phi}=\rho cos(\phi), \frac{dy}{dz}=0$ $\frac{dz}{d \rho}=0,\frac{dz}{d \phi}=0, \frac{dz}{dz}=1$ And then dot product my vector with each of rho, phi and z components. But I've found in wikipedia that there's no rho in the derivative with respect to phi...? http://en.wikipedia.org/wiki/Vector_...al_coordinates The same thing for the cartesian to spherical. b) If I want to convert a vector from cylindrical/spherical to cartesian, do I have to take the same approach as a)? c) How can I convert unit vectors between cylindrical and spherical and vice versa?