Convert to cylindrical coordinates

In summary, the given expression can be evaluated by converting to cylindrical coordinates with limits of integration from 0 to pi for theta, 0 to 1 for r, and r^2 to r for z. The resulting integral is (rcos\theta sin\theta z) r dzdrd\theta. The limits of theta are from 0 to pi/2 as neither x nor y can be negative.
  • #1
caliguy
4
0
Evaluate by changing to cylindrical coordinates

[tex]\int[/tex] from 0 to 1 [tex]\int[/tex] from 0 to (1-y^2)^1/2 [tex]\int[/tex] from (x^2+y^2) to (x^2+y^2)^1/2 (xyz) dzdxdy

I came to an answer of integral from 0 to pi integral from 0 to 1 integral from r^2 to r (rcos[tex]\theta[/tex]rsin[tex]\theta[/tex]z) r dzdrd[tex]\theta[/tex]
Is this the correct answer?
 
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  • #2
Hello Caliguy. Click on the expression below to see how to post it so it is readable in tex:

[tex]\int_0^1 \int_0^{\sqrt{1-y^2}}\int_{x^2+y^2}^{\sqrt{x^2+y^2}}xyz\ dzdxdy[/tex]

This looks like a first octant integral. Check your [itex]\theta[/itex] limits.
 
  • #3
To me they seem right, doesn't theta go from zero to pi? after graphing it it looks like a half a circle... maybe I'm overlooking something?
 
  • #4
Neither x nor y get negative in your original integrals.
 
  • #5
So theta only goes from 0 to pi/2 right?
 
  • #6
caliguy said:
So theta only goes from 0 to pi/2 right?

Yes.
 

What is the purpose of converting to cylindrical coordinates?

The purpose of converting to cylindrical coordinates is to describe a point or object in three-dimensional space using a combination of distance from a central point, angle from a reference plane, and height from a reference plane.

How do you convert from Cartesian coordinates to cylindrical coordinates?

To convert from Cartesian coordinates (x, y, z) to cylindrical coordinates (r, θ, z), you can use the following equations:
r = √(x² + y²)
θ = tan⁻¹(y/x)
z = z

What are the differences between cylindrical and spherical coordinates?

Cylindrical coordinates use two angles (θ and z) and one distance (r) to describe a point in 3D space, while spherical coordinates use two angles (θ and φ) and one distance (ρ). Additionally, cylindrical coordinates are often used for objects with cylindrical symmetry, while spherical coordinates are used for objects with spherical symmetry.

What are some real-life applications of cylindrical coordinates?

Cylindrical coordinates are commonly used in engineering and physics, such as in the analysis of cylindrical objects like pipes or cylinders. They are also used in navigation and astronomy to describe the position of objects in space.

Can cylindrical coordinates be converted back to Cartesian coordinates?

Yes, cylindrical coordinates can be converted back to Cartesian coordinates using the following equations:
x = rcosθ
y = rsinθ
z = z

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