Evaluate the triple integral (with spherical coordinates)

In summary, the person is asking for help with a problem in spherical coordinates involving the integral of e^-sqrt(x^2+y^2+z^2) and is unsure how to determine the intervals for theta and phi. They are then given an explanation of how to determine the intervals for these angles.
  • #1
melihaltintas
6
0

Homework Statement


Firstly sorry for my bad english,i have a one question for you(İ try it but i didn't solve it )

Homework Equations


The Attempt at a Solution


i know problem will be solved spherical coordinates but i don't know how i get angles (interval) theta and fi ?
[tex]\int_{0}^{\infty}\int_{0}^{\infty}\int_{0}^{\infty}e^{-\sqrt{x^2+y^2+z^2}}\,dxdydz[/tex]

Mod note: Fixed LaTeX. Read what tiny-tim said below.
 
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  • #2


You get the angles by thinking about what the spherical coordinate variables mean. [itex]\phi[/itex] is the angle from the positive z-axis to the negative x-axis and, to cover all space, would normally go from [itex]0[/itex] to [itex]\pi[/itex]. Since you want z to stay positive, you want [itex]\phi[/itex] to go from [itex]0[/itex] to [itex]\pi/2[/itex]. [itex]\theta[/itex] goes around a complete circle in the xy-plane in going from [itex]0[/itex] to [itex]2\pi[/itex]. Since the first quadrant is 1/4 of that, [itex]\theta[/itex] goes from [itex]0[/itex] to [itex]\pi/2[/itex]. Finally, there is no upper limit on the distance from the origin to any point in the first octant so [itex]\rho[/itex] goes from [itex]0[/itex] to [itex]\infty[/itex].
 
  • #3
welcome to pf!

hi melihaltintas! welcome to pf! :smile:

don't try to put forum tags inside latex! :wink: …​
melihaltintas said:
[tex]\int_{0}^{\infty}\int_{0}^{ \infty}\int_{0}^{\infty}e^{-\sqrt{x^2+y^2+ z^2}}\,dxdydz[/tex]
 
  • #4
thanks a lot :)
 

1. What are spherical coordinates?

Spherical coordinates are a system of coordinates used to locate points in three-dimensional space. They consist of a radial distance from the origin, an angle from the positive z-axis called the inclination or polar angle, and an angle from the positive x-axis called the azimuth or longitudinal angle.

2. How do you convert from Cartesian coordinates to spherical coordinates?

To convert from Cartesian coordinates (x, y, z) to spherical coordinates (r, θ, φ), you can use the following formulas: r = √(x² + y² + z²), θ = arccos(z/r), and φ = arctan(y/x). The angles θ and φ are typically measured in radians.

3. What is the purpose of using spherical coordinates in a triple integral?

Spherical coordinates are useful for evaluating triple integrals in cases where the region of integration is better described in terms of radial distance and angles rather than x, y, and z coordinates. They can also simplify the calculation of integrals involving spherical objects or functions with spherical symmetry.

4. How do you set up the limits of integration for a triple integral in spherical coordinates?

In spherical coordinates, the limits of integration for the radial distance r are typically from 0 to the maximum value of r in the region of integration. The inclination angle θ is typically integrated from 0 to π, and the azimuth angle φ is typically integrated from 0 to 2π. However, these limits may vary depending on the specific region being integrated.

5. What are some common applications of triple integrals with spherical coordinates?

Triple integrals with spherical coordinates are commonly used in physics and engineering to solve problems involving symmetrical three-dimensional objects, such as finding the volume or mass of a sphere or calculating the electric field within a charged sphere. They are also used in mathematics to evaluate triple integrals involving spherical functions, such as the Laplace or Poisson equations.

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