Cartesian unit vectors expressed by Cylindrical unit vectors

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SUMMARY

The discussion focuses on expressing Cartesian unit vectors in terms of cylindrical unit vectors using matrix transformations. Specifically, the transformation is represented by the matrix $$ \begin{bmatrix} cos(\phi) & sin(\phi) \\ -sin(\phi) & cos(\phi) \end{bmatrix} $$, which relates the cylindrical unit vectors $$ \begin{bmatrix} \hat{\rho} \\ \hat{\phi} \end{bmatrix} $$ to Cartesian unit vectors $$ \begin{bmatrix} \hat{i} \\ \hat{j} \end{bmatrix} $$. The inverse matrix is also provided as $$ \begin{bmatrix} cos(\phi) & -sin(\phi) \\ -sin(\phi) & cos(\phi) \end{bmatrix} $$, allowing for the conversion back to Cartesian coordinates. This matrix approach offers a clear geometric understanding of the transformation.

PREREQUISITES
  • Understanding of Cartesian and cylindrical coordinate systems
  • Familiarity with matrix operations and transformations
  • Knowledge of trigonometric functions, specifically sine and cosine
  • Basic concepts of vector representation in physics
NEXT STEPS
  • Study matrix transformations in linear algebra
  • Explore the geometric interpretation of coordinate transformations
  • Learn about the applications of cylindrical coordinates in physics
  • Investigate the use of unit vectors in vector calculus
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Students and professionals in physics, mathematics, and engineering who are working with coordinate transformations and vector analysis will benefit from this discussion.

chenrim
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please someone explain me the following expression for Cartesian unit vectors expressed by the cylindrical unit vectors:

http://web.mit.edu/8.02t/www/materials/modules/ReviewB.pdf
at page B-8 line B.2.4

i would like to know which steps led to it.

thanks,

Chen
 
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chenrim said:
please someone explain me the following expression for Cartesian unit vectors expressed by the cylindrical unit vectors:

http://web.mit.edu/8.02t/www/materials/modules/ReviewB.pdf
at page B-8 line B.2.4

i would like to know which steps led to it.

thanks,

Chen
One way to think of this is in terms of matrices:
$$ \begin{bmatrix} \hat{\rho} \\ \hat{\phi} \end{bmatrix} = \begin{bmatrix} cos(\phi) & sin(\phi) \\ -sin(\phi) & cos(\phi) \end{bmatrix} \begin{bmatrix} \hat{i} \\ \hat{j}\end{bmatrix}$$
Apply the inverse of the above matrix to get a vector with the unit vectors i and j. The inverse is:
$$\begin{bmatrix} cos(\phi) & -sin(\phi) \\ -sin(\phi) & cos(\phi) \end{bmatrix} $$
 
I tried to understand it by the geometry of it
but that's a better way to understand it.

Thanks
 

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