Proof - Express in Clyndrical Coordinates

In summary, when expressing ds^2 = dx^2 + dy^2 +dz^2 in cylindrical coordinates, the resulting equation is ds^2 = dr^2 + r^2d^2 + dz^2. The notation should be interpreted as (dx)^2 instead of dx^2.
  • #1
forestmine
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Proof -- Express in Clyndrical Coordinates

Homework Statement



Show that when you express ds^2 = dx^2 + dy^2 +dz^2 in cylindrical coordinates, you get ds^2 = dr^2 + r^2d^2 + dz^2.

Homework Equations



x=rcosθ
y=rsinθ
z=z

The Attempt at a Solution



EDIT// I was really over thinking this...think I've got it figured out. Thanks anyways!

I'm somewhat confused about the notation here and how to really go about this. My first thought was just to plug in some values...

ds^2 = d(r^2*cos^2(θ)) + d(r^2*sin^2(θ)) + dz^2

The d(__) are really throwing me off here. I don't see how the second term in the right hand side of the proof goes to r^2d^2.

Ah really lost here. Just need some help in the right direction.

Thank you!
 
Last edited:
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  • #2


You should interpret [itex]dx^2[/itex] as meaning [itex](dx)^2[/itex].
 
  • #3


I think that was my hang up exactly. Thanks!
 

1. What are cylindrical coordinates?

Cylindrical coordinates are a system of coordinates that describe the position of a point in three-dimensional space using distance, angle, and height. The distance is represented by the radius from the origin, the angle is measured from a fixed reference direction, and the height is the perpendicular distance from the point to a fixed plane.

2. How do you express coordinates in cylindrical coordinates?

To express coordinates in cylindrical coordinates, you use the notation (r, θ, z), where r is the distance from the origin, θ is the angle from a fixed reference direction, and z is the height or displacement from a fixed plane.

3. What is the relationship between cylindrical coordinates and Cartesian coordinates?

Cylindrical coordinates are closely related to Cartesian coordinates. The distance r in cylindrical coordinates is equivalent to the hypotenuse of a right triangle formed by the x and y coordinates in Cartesian coordinates. The angle θ is the same in both systems, and the height z is equivalent to the z coordinate in Cartesian coordinates.

4. How do you convert from cylindrical coordinates to Cartesian coordinates?

To convert from cylindrical coordinates to Cartesian coordinates, you use the following equations: x = rcos(θ), y = rsin(θ), and z = z. These equations express the same point in both systems, with x and y representing the horizontal and vertical coordinates, and z representing the height.

5. What is the significance of expressing coordinates in different coordinate systems?

Expressing coordinates in different coordinate systems allows us to describe the same point in various ways, making it easier to solve problems and analyze data. Cylindrical coordinates are particularly useful when dealing with objects that have rotational symmetry, as they can simplify calculations and provide a more intuitive representation of the object's position.

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