Cartesian unit vectors in terms of cylindrical vectors

In summary, the conversation discusses how to express ex, ey, and ez in terms of er, eθ, and eZ. This involves using a drawing with er at an angle θ relative to ex and eθ perpendicular to er to find the projections of ex on er and eθ. This method should result in ex being equal to cosθer - sinθeθ.
  • #1
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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  • #2
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.
 

What are Cartesian unit vectors?

Cartesian unit vectors are three orthogonal vectors (i, j, k) that represent the three dimensions of a Cartesian coordinate system. These vectors have a magnitude of 1 and are used to describe the direction and orientation of a point or vector in space.

What are cylindrical vectors?

Cylindrical vectors are a set of three vectors (ρ, φ, z) used in cylindrical coordinate systems to describe the position and orientation of a point or vector in space. The ρ vector represents the distance from the origin, the φ vector represents the angle from a reference plane, and the z vector represents the height or depth.

How do Cartesian unit vectors relate to cylindrical vectors?

Cartesian unit vectors can be converted into cylindrical vectors using trigonometric functions. The ρ vector is equivalent to the x and y components of the Cartesian vector, while the φ vector is equivalent to the angle between the Cartesian x-y plane and the cylindrical ρ vector. The z vector remains the same in both coordinate systems.

What is the relationship between the magnitudes of Cartesian unit vectors and cylindrical vectors?

The magnitudes of Cartesian unit vectors and cylindrical vectors are equal. This means that the length of the Cartesian unit vector (i, j, k) is equal to the length of the cylindrical vector (ρ, φ, z). Both have a magnitude of 1.

Can cylindrical vectors be converted back to Cartesian unit vectors?

Yes, cylindrical vectors can be converted back to Cartesian unit vectors using the same trigonometric functions. The x and y components can be found using the ρ and φ vectors, and the z component remains the same. The resulting Cartesian unit vector will have a magnitude of 1 and represent the same direction and orientation in space.

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