Converting vector in cartesian to cylindrical coordinates












2














This seems like a trivial question, and I'm just not sure if I'm doing it right.

I have vector in cartesian coordinate system: $vec{N} =yvec{a_x} −2xvec{a_y} + yvec{a_z}$. And I need to represent it in cylindrical coord.

Relevant equations:
$$A_rho=A_xcosphi+A_ysinphi$$
$$A_phi=−A_xsinphi+A_ycosphi$$
$$A_z=A_z$$

What is cofusing me is this: The formula for $phi$ is $phi=arctan(frac{y}{x})$ .
Are those $x$ and $y$ in fact $a_x$ and $a_y$? If so, then for my problem, wouldn't it be $phi=arctan(frac{-2x}{y})$? And do I need to change the unit vectors too?










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    2














    This seems like a trivial question, and I'm just not sure if I'm doing it right.

    I have vector in cartesian coordinate system: $vec{N} =yvec{a_x} −2xvec{a_y} + yvec{a_z}$. And I need to represent it in cylindrical coord.

    Relevant equations:
    $$A_rho=A_xcosphi+A_ysinphi$$
    $$A_phi=−A_xsinphi+A_ycosphi$$
    $$A_z=A_z$$

    What is cofusing me is this: The formula for $phi$ is $phi=arctan(frac{y}{x})$ .
    Are those $x$ and $y$ in fact $a_x$ and $a_y$? If so, then for my problem, wouldn't it be $phi=arctan(frac{-2x}{y})$? And do I need to change the unit vectors too?










    share|cite|improve this question



























      2












      2








      2







      This seems like a trivial question, and I'm just not sure if I'm doing it right.

      I have vector in cartesian coordinate system: $vec{N} =yvec{a_x} −2xvec{a_y} + yvec{a_z}$. And I need to represent it in cylindrical coord.

      Relevant equations:
      $$A_rho=A_xcosphi+A_ysinphi$$
      $$A_phi=−A_xsinphi+A_ycosphi$$
      $$A_z=A_z$$

      What is cofusing me is this: The formula for $phi$ is $phi=arctan(frac{y}{x})$ .
      Are those $x$ and $y$ in fact $a_x$ and $a_y$? If so, then for my problem, wouldn't it be $phi=arctan(frac{-2x}{y})$? And do I need to change the unit vectors too?










      share|cite|improve this question















      This seems like a trivial question, and I'm just not sure if I'm doing it right.

      I have vector in cartesian coordinate system: $vec{N} =yvec{a_x} −2xvec{a_y} + yvec{a_z}$. And I need to represent it in cylindrical coord.

      Relevant equations:
      $$A_rho=A_xcosphi+A_ysinphi$$
      $$A_phi=−A_xsinphi+A_ycosphi$$
      $$A_z=A_z$$

      What is cofusing me is this: The formula for $phi$ is $phi=arctan(frac{y}{x})$ .
      Are those $x$ and $y$ in fact $a_x$ and $a_y$? If so, then for my problem, wouldn't it be $phi=arctan(frac{-2x}{y})$? And do I need to change the unit vectors too?







      vectors coordinate-systems






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      edited Mar 17 '17 at 0:08









      Community

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      asked Jun 13 '15 at 23:22









      user247996user247996

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          A vector field is defined over a region in space $mathbb{R}^3 :$ $(x,y,z)$ or $(r,phi, z)$, whichever coordinate system you may choose to represent this space. Your vector $vec{N}$ should be defined in this space at a position vector $vec{r} = (x,y,z)$ or $(r,phi, z)$. So you need to find



          $phi = arctan left( frac{y}{x} right)$



          Simply put: A vector field without reference to its position makes no sense in a transformation of coordinates.






          share|cite|improve this answer





















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            A vector field is defined over a region in space $mathbb{R}^3 :$ $(x,y,z)$ or $(r,phi, z)$, whichever coordinate system you may choose to represent this space. Your vector $vec{N}$ should be defined in this space at a position vector $vec{r} = (x,y,z)$ or $(r,phi, z)$. So you need to find



            $phi = arctan left( frac{y}{x} right)$



            Simply put: A vector field without reference to its position makes no sense in a transformation of coordinates.






            share|cite|improve this answer


























              0














              A vector field is defined over a region in space $mathbb{R}^3 :$ $(x,y,z)$ or $(r,phi, z)$, whichever coordinate system you may choose to represent this space. Your vector $vec{N}$ should be defined in this space at a position vector $vec{r} = (x,y,z)$ or $(r,phi, z)$. So you need to find



              $phi = arctan left( frac{y}{x} right)$



              Simply put: A vector field without reference to its position makes no sense in a transformation of coordinates.






              share|cite|improve this answer
























                0












                0








                0






                A vector field is defined over a region in space $mathbb{R}^3 :$ $(x,y,z)$ or $(r,phi, z)$, whichever coordinate system you may choose to represent this space. Your vector $vec{N}$ should be defined in this space at a position vector $vec{r} = (x,y,z)$ or $(r,phi, z)$. So you need to find



                $phi = arctan left( frac{y}{x} right)$



                Simply put: A vector field without reference to its position makes no sense in a transformation of coordinates.






                share|cite|improve this answer












                A vector field is defined over a region in space $mathbb{R}^3 :$ $(x,y,z)$ or $(r,phi, z)$, whichever coordinate system you may choose to represent this space. Your vector $vec{N}$ should be defined in this space at a position vector $vec{r} = (x,y,z)$ or $(r,phi, z)$. So you need to find



                $phi = arctan left( frac{y}{x} right)$



                Simply put: A vector field without reference to its position makes no sense in a transformation of coordinates.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Sep 21 '18 at 8:37









                muralymuraly

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