Calculating the volume of a sphere after switching to spherical coordinates?












7














I used the code in the second answer on this page to switch from Cartesian to Spherical coordinates and integrate a function over the sphere. I would like to use this code to calculate the volume of a sphere. However if I set $ f(x, y, z) = 1 $, I get the following output:




$ -frac{1}{3}r^3 varphicos(theta) $




Here is the code I used:



Needs["VectorAnalysis`"]

JacobianDeterminant[Spherical[r, θ, ϕ]]

f[x_, y_, z_] := 1

Integrate[
f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[
Spherical @@ #] &@{r, θ, ϕ},
r, θ, ϕ]


How can I make the code return the volume of a sphere which is $frac{4}{3}pi r^3$?










share|improve this question





























    7














    I used the code in the second answer on this page to switch from Cartesian to Spherical coordinates and integrate a function over the sphere. I would like to use this code to calculate the volume of a sphere. However if I set $ f(x, y, z) = 1 $, I get the following output:




    $ -frac{1}{3}r^3 varphicos(theta) $




    Here is the code I used:



    Needs["VectorAnalysis`"]

    JacobianDeterminant[Spherical[r, θ, ϕ]]

    f[x_, y_, z_] := 1

    Integrate[
    f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[
    Spherical @@ #] &@{r, θ, ϕ},
    r, θ, ϕ]


    How can I make the code return the volume of a sphere which is $frac{4}{3}pi r^3$?










    share|improve this question



























      7












      7








      7







      I used the code in the second answer on this page to switch from Cartesian to Spherical coordinates and integrate a function over the sphere. I would like to use this code to calculate the volume of a sphere. However if I set $ f(x, y, z) = 1 $, I get the following output:




      $ -frac{1}{3}r^3 varphicos(theta) $




      Here is the code I used:



      Needs["VectorAnalysis`"]

      JacobianDeterminant[Spherical[r, θ, ϕ]]

      f[x_, y_, z_] := 1

      Integrate[
      f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[
      Spherical @@ #] &@{r, θ, ϕ},
      r, θ, ϕ]


      How can I make the code return the volume of a sphere which is $frac{4}{3}pi r^3$?










      share|improve this question















      I used the code in the second answer on this page to switch from Cartesian to Spherical coordinates and integrate a function over the sphere. I would like to use this code to calculate the volume of a sphere. However if I set $ f(x, y, z) = 1 $, I get the following output:




      $ -frac{1}{3}r^3 varphicos(theta) $




      Here is the code I used:



      Needs["VectorAnalysis`"]

      JacobianDeterminant[Spherical[r, θ, ϕ]]

      f[x_, y_, z_] := 1

      Integrate[
      f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[
      Spherical @@ #] &@{r, θ, ϕ},
      r, θ, ϕ]


      How can I make the code return the volume of a sphere which is $frac{4}{3}pi r^3$?







      calculus-and-analysis coordinate-transformation






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Dec 12 '18 at 12:25









      Αλέξανδρος Ζεγγ

      4,0441928




      4,0441928










      asked Dec 12 '18 at 11:48









      sonicboom

      1383




      1383






















          2 Answers
          2






          active

          oldest

          votes


















          10














          Employing most of your own code;



          Integrate[
          f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[Spherical @@ #] &@{r, θ, ϕ},
          {r, 0, R}, {θ, 0, π}, {ϕ, -π, π}
          ]



          (4 π R^3)/3




          That is, you just have to add the integral boundaries.






          share|improve this answer































            5














            Try this



            transform[f : (_Function | _Symbol), coordi_: {x, y, z}, coordf_: {r, θ, ϕ}] := Module[{rules, jdet},
            rules = Thread[coordi -> CoordinateTransformData["Spherical" -> "Cartesian", "Mapping", coordf]];
            jdet = CoordinateTransformData["Spherical" -> "Cartesian", "MappingJacobianDeterminant", coordf];
            jdet f @@ coordi /. rules
            ]

            f[x_, y_, z_] := 1

            Integrate[transform[f], r, {θ, 0, π}, {ϕ, 0, 2 π}]



            (4 π r^3)/3






            share|improve this answer























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              2 Answers
              2






              active

              oldest

              votes








              2 Answers
              2






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              10














              Employing most of your own code;



              Integrate[
              f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[Spherical @@ #] &@{r, θ, ϕ},
              {r, 0, R}, {θ, 0, π}, {ϕ, -π, π}
              ]



              (4 π R^3)/3




              That is, you just have to add the integral boundaries.






              share|improve this answer




























                10














                Employing most of your own code;



                Integrate[
                f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[Spherical @@ #] &@{r, θ, ϕ},
                {r, 0, R}, {θ, 0, π}, {ϕ, -π, π}
                ]



                (4 π R^3)/3




                That is, you just have to add the integral boundaries.






                share|improve this answer


























                  10












                  10








                  10






                  Employing most of your own code;



                  Integrate[
                  f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[Spherical @@ #] &@{r, θ, ϕ},
                  {r, 0, R}, {θ, 0, π}, {ϕ, -π, π}
                  ]



                  (4 π R^3)/3




                  That is, you just have to add the integral boundaries.






                  share|improve this answer














                  Employing most of your own code;



                  Integrate[
                  f @@ CoordinatesToCartesian[#, Spherical @@ #] JacobianDeterminant[Spherical @@ #] &@{r, θ, ϕ},
                  {r, 0, R}, {θ, 0, π}, {ϕ, -π, π}
                  ]



                  (4 π R^3)/3




                  That is, you just have to add the integral boundaries.







                  share|improve this answer














                  share|improve this answer



                  share|improve this answer








                  edited Dec 12 '18 at 19:02

























                  answered Dec 12 '18 at 12:41









                  Henrik Schumacher

                  48.8k467139




                  48.8k467139























                      5














                      Try this



                      transform[f : (_Function | _Symbol), coordi_: {x, y, z}, coordf_: {r, θ, ϕ}] := Module[{rules, jdet},
                      rules = Thread[coordi -> CoordinateTransformData["Spherical" -> "Cartesian", "Mapping", coordf]];
                      jdet = CoordinateTransformData["Spherical" -> "Cartesian", "MappingJacobianDeterminant", coordf];
                      jdet f @@ coordi /. rules
                      ]

                      f[x_, y_, z_] := 1

                      Integrate[transform[f], r, {θ, 0, π}, {ϕ, 0, 2 π}]



                      (4 π r^3)/3






                      share|improve this answer




























                        5














                        Try this



                        transform[f : (_Function | _Symbol), coordi_: {x, y, z}, coordf_: {r, θ, ϕ}] := Module[{rules, jdet},
                        rules = Thread[coordi -> CoordinateTransformData["Spherical" -> "Cartesian", "Mapping", coordf]];
                        jdet = CoordinateTransformData["Spherical" -> "Cartesian", "MappingJacobianDeterminant", coordf];
                        jdet f @@ coordi /. rules
                        ]

                        f[x_, y_, z_] := 1

                        Integrate[transform[f], r, {θ, 0, π}, {ϕ, 0, 2 π}]



                        (4 π r^3)/3






                        share|improve this answer


























                          5












                          5








                          5






                          Try this



                          transform[f : (_Function | _Symbol), coordi_: {x, y, z}, coordf_: {r, θ, ϕ}] := Module[{rules, jdet},
                          rules = Thread[coordi -> CoordinateTransformData["Spherical" -> "Cartesian", "Mapping", coordf]];
                          jdet = CoordinateTransformData["Spherical" -> "Cartesian", "MappingJacobianDeterminant", coordf];
                          jdet f @@ coordi /. rules
                          ]

                          f[x_, y_, z_] := 1

                          Integrate[transform[f], r, {θ, 0, π}, {ϕ, 0, 2 π}]



                          (4 π r^3)/3






                          share|improve this answer














                          Try this



                          transform[f : (_Function | _Symbol), coordi_: {x, y, z}, coordf_: {r, θ, ϕ}] := Module[{rules, jdet},
                          rules = Thread[coordi -> CoordinateTransformData["Spherical" -> "Cartesian", "Mapping", coordf]];
                          jdet = CoordinateTransformData["Spherical" -> "Cartesian", "MappingJacobianDeterminant", coordf];
                          jdet f @@ coordi /. rules
                          ]

                          f[x_, y_, z_] := 1

                          Integrate[transform[f], r, {θ, 0, π}, {ϕ, 0, 2 π}]



                          (4 π r^3)/3







                          share|improve this answer














                          share|improve this answer



                          share|improve this answer








                          edited Dec 12 '18 at 12:41

























                          answered Dec 12 '18 at 12:40









                          Αλέξανδρος Ζεγγ

                          4,0441928




                          4,0441928






























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