Cartesian unit vectors in terms of cylindrical vectors

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SUMMARY

The discussion focuses on expressing Cartesian unit vectors (ex, ey, ez) in terms of cylindrical unit vectors (er, eθ, eZ). The transformation involves using the relationships r = (x² + y²)^(1/2) and θ = arctan(y/x). The key conclusion is that ex can be expressed as ex = cos(θ)er - (sin(θ)/r)eθ, which is derived from the partial derivative of A with respect to x. The participants emphasize the importance of visualizing the vectors to understand their projections accurately.

PREREQUISITES
  • Understanding of Cartesian and cylindrical coordinate systems
  • Familiarity with vector calculus and partial derivatives
  • Knowledge of trigonometric functions and their applications in vector projections
  • Ability to interpret graphical representations of vectors
NEXT STEPS
  • Study vector transformations between Cartesian and cylindrical coordinates
  • Learn about the geometric interpretation of unit vectors in different coordinate systems
  • Explore the applications of partial derivatives in physics and engineering
  • Investigate the use of graphical methods to visualize vector projections
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Students and professionals in physics, engineering, and mathematics who are working with vector calculus and coordinate transformations will benefit from this discussion.

Komekami
How do I express ex,ey,ez in terms er,eθ,eZ?
r=(x^2+y^2)^1/2,θ=arctan(y/x),Z=z
A(r,θ,z)
∂A/∂x=x/(x^2+y^2)^1/2er+(-y)/(x^2+y^2)eθ=cosθer-(sinθ/r)eθ
ex=(∂A/∂x)/|∂A/∂x| I should get ex as cosθer-sinθeθ, but I don't get ex correctly.
am i doing this wrong?
 
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Komekami said:
How do I express ex,ey,ez in terms er,eθ,eZ?
Make yourself a drawing with ##\hat{e}_x## horizontal and ##\hat{e}_y## vertical. In this drawing add ##\hat{e}_r## at angle ##\theta## w.r.t. ##\hat{e}_x##. Add ##\hat{e}_{\theta}## perpendicular to ##\hat{e}_r##. Study the drawing and find the projections of ##\hat{e}_x## on ##\hat{e}_r## and ##\hat{e}_{\theta}##. You should get what you expect to get.
 

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