How to find volume and surface area of a spindle torus?












2












$begingroup$


I know that you can use the formulas described in Pappus' centroid theorem, detailed here. But does Pappus' centroid theorem hold true for all forms of a torus: ring, horn, and spindle? I found another website that uses Pappus' centroid theorem for the volume and surface area of a ring or horn torus, but a different formula for the spindle torus.



This is the formula listed for the spindle torus:
$$
V = frac23 pi ( 2r^2 + R^2 ) sqrt{r^2 - R^2} + pi r^2 R left[pi + 2arctanleft( frac{R}{sqrt{r^2 - R^2}} right) right]
$$

where $r$ is the minor radius and $R$ is the major radius.



Is this formula for the spindle torus' volume accurate, or do I just have to use Pappus' centroid theorem?










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    2












    $begingroup$


    I know that you can use the formulas described in Pappus' centroid theorem, detailed here. But does Pappus' centroid theorem hold true for all forms of a torus: ring, horn, and spindle? I found another website that uses Pappus' centroid theorem for the volume and surface area of a ring or horn torus, but a different formula for the spindle torus.



    This is the formula listed for the spindle torus:
    $$
    V = frac23 pi ( 2r^2 + R^2 ) sqrt{r^2 - R^2} + pi r^2 R left[pi + 2arctanleft( frac{R}{sqrt{r^2 - R^2}} right) right]
    $$

    where $r$ is the minor radius and $R$ is the major radius.



    Is this formula for the spindle torus' volume accurate, or do I just have to use Pappus' centroid theorem?










    share|cite|improve this question











    $endgroup$















      2












      2








      2





      $begingroup$


      I know that you can use the formulas described in Pappus' centroid theorem, detailed here. But does Pappus' centroid theorem hold true for all forms of a torus: ring, horn, and spindle? I found another website that uses Pappus' centroid theorem for the volume and surface area of a ring or horn torus, but a different formula for the spindle torus.



      This is the formula listed for the spindle torus:
      $$
      V = frac23 pi ( 2r^2 + R^2 ) sqrt{r^2 - R^2} + pi r^2 R left[pi + 2arctanleft( frac{R}{sqrt{r^2 - R^2}} right) right]
      $$

      where $r$ is the minor radius and $R$ is the major radius.



      Is this formula for the spindle torus' volume accurate, or do I just have to use Pappus' centroid theorem?










      share|cite|improve this question











      $endgroup$




      I know that you can use the formulas described in Pappus' centroid theorem, detailed here. But does Pappus' centroid theorem hold true for all forms of a torus: ring, horn, and spindle? I found another website that uses Pappus' centroid theorem for the volume and surface area of a ring or horn torus, but a different formula for the spindle torus.



      This is the formula listed for the spindle torus:
      $$
      V = frac23 pi ( 2r^2 + R^2 ) sqrt{r^2 - R^2} + pi r^2 R left[pi + 2arctanleft( frac{R}{sqrt{r^2 - R^2}} right) right]
      $$

      where $r$ is the minor radius and $R$ is the major radius.



      Is this formula for the spindle torus' volume accurate, or do I just have to use Pappus' centroid theorem?







      calculus area volume solid-of-revolution






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      share|cite|improve this question













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      edited Dec 10 '18 at 11:58









      Brahadeesh

      6,24242361




      6,24242361










      asked Dec 10 '18 at 11:46









      fi12fi12

      1113




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