Showing that the surface area of a zone of a sphere that lies between two parallel planes is $2pi Rh$











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Show that the surface area of a zone of a sphere that lies
between two parallel planes is $2pi Rh$,



Where $R$ is the radius of the sphere and $h$ is the distance between the
planes.



If you are wondering what is interesting about this ?



The fact that the surface area depends only on distance between the planes, and not where they cut the sphere.



I am looking to understand a calculus based solution.










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  • Check mathworld.wolfram.com/Zone.html
    – Macavity
    Oct 13 '14 at 6:13










  • i looked at it, its complicated, is there an easy way to do it, may be by using parameters
    – Fusion2
    Oct 13 '14 at 6:29






  • 2




    @KittenButcher The presented solution is using "parameters" and uses some basic calculus and integration. You should instead try to work through the solution and ask a question about a particular part of the presented proof.
    – AlexR
    Oct 13 '14 at 6:32










  • You can use calculus to find the surface area of a spherical cap and then subtract.
    – Michael Burr
    Aug 24 '17 at 11:43















up vote
1
down vote

favorite












Show that the surface area of a zone of a sphere that lies
between two parallel planes is $2pi Rh$,



Where $R$ is the radius of the sphere and $h$ is the distance between the
planes.



If you are wondering what is interesting about this ?



The fact that the surface area depends only on distance between the planes, and not where they cut the sphere.



I am looking to understand a calculus based solution.










share|cite|improve this question
















bumped to the homepage by Community 14 hours ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.















  • Check mathworld.wolfram.com/Zone.html
    – Macavity
    Oct 13 '14 at 6:13










  • i looked at it, its complicated, is there an easy way to do it, may be by using parameters
    – Fusion2
    Oct 13 '14 at 6:29






  • 2




    @KittenButcher The presented solution is using "parameters" and uses some basic calculus and integration. You should instead try to work through the solution and ask a question about a particular part of the presented proof.
    – AlexR
    Oct 13 '14 at 6:32










  • You can use calculus to find the surface area of a spherical cap and then subtract.
    – Michael Burr
    Aug 24 '17 at 11:43













up vote
1
down vote

favorite









up vote
1
down vote

favorite











Show that the surface area of a zone of a sphere that lies
between two parallel planes is $2pi Rh$,



Where $R$ is the radius of the sphere and $h$ is the distance between the
planes.



If you are wondering what is interesting about this ?



The fact that the surface area depends only on distance between the planes, and not where they cut the sphere.



I am looking to understand a calculus based solution.










share|cite|improve this question















Show that the surface area of a zone of a sphere that lies
between two parallel planes is $2pi Rh$,



Where $R$ is the radius of the sphere and $h$ is the distance between the
planes.



If you are wondering what is interesting about this ?



The fact that the surface area depends only on distance between the planes, and not where they cut the sphere.



I am looking to understand a calculus based solution.







calculus integration






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share|cite|improve this question













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edited Feb 7 at 1:03









Matthew Conroy

10.2k32836




10.2k32836










asked Oct 13 '14 at 6:05









Fusion2

34418




34418





bumped to the homepage by Community 14 hours ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.







bumped to the homepage by Community 14 hours ago


This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.














  • Check mathworld.wolfram.com/Zone.html
    – Macavity
    Oct 13 '14 at 6:13










  • i looked at it, its complicated, is there an easy way to do it, may be by using parameters
    – Fusion2
    Oct 13 '14 at 6:29






  • 2




    @KittenButcher The presented solution is using "parameters" and uses some basic calculus and integration. You should instead try to work through the solution and ask a question about a particular part of the presented proof.
    – AlexR
    Oct 13 '14 at 6:32










  • You can use calculus to find the surface area of a spherical cap and then subtract.
    – Michael Burr
    Aug 24 '17 at 11:43


















  • Check mathworld.wolfram.com/Zone.html
    – Macavity
    Oct 13 '14 at 6:13










  • i looked at it, its complicated, is there an easy way to do it, may be by using parameters
    – Fusion2
    Oct 13 '14 at 6:29






  • 2




    @KittenButcher The presented solution is using "parameters" and uses some basic calculus and integration. You should instead try to work through the solution and ask a question about a particular part of the presented proof.
    – AlexR
    Oct 13 '14 at 6:32










  • You can use calculus to find the surface area of a spherical cap and then subtract.
    – Michael Burr
    Aug 24 '17 at 11:43
















Check mathworld.wolfram.com/Zone.html
– Macavity
Oct 13 '14 at 6:13




Check mathworld.wolfram.com/Zone.html
– Macavity
Oct 13 '14 at 6:13












i looked at it, its complicated, is there an easy way to do it, may be by using parameters
– Fusion2
Oct 13 '14 at 6:29




i looked at it, its complicated, is there an easy way to do it, may be by using parameters
– Fusion2
Oct 13 '14 at 6:29




2




2




@KittenButcher The presented solution is using "parameters" and uses some basic calculus and integration. You should instead try to work through the solution and ask a question about a particular part of the presented proof.
– AlexR
Oct 13 '14 at 6:32




@KittenButcher The presented solution is using "parameters" and uses some basic calculus and integration. You should instead try to work through the solution and ask a question about a particular part of the presented proof.
– AlexR
Oct 13 '14 at 6:32












You can use calculus to find the surface area of a spherical cap and then subtract.
– Michael Burr
Aug 24 '17 at 11:43




You can use calculus to find the surface area of a spherical cap and then subtract.
– Michael Burr
Aug 24 '17 at 11:43










2 Answers
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A sphere is generated by rotating the right portion of a circle centered at the origin and with radius R about the y-axis, that is, by rotating the curve x=√R^2-y^2 about the y-axis, so the surface area of the required zone would be ∫ (from -c to c) 2π*√R^2-y^2*√R^2/R^2-y^2 dy, now we know that 2c=h( assume that c>0), we got h*∫ 2πR dy=2πRh






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  • Please use MathJax.
    – José Carlos Santos
    Aug 24 '17 at 10:24


















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0
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Consider an "infinitesimal latitude annulus" $A$ of geographical width $Deltatheta$, positioned at the geographical latitude $thetainleft]-{piover2},{piover2}right[$. Its area is given by
$${rm area}(A)=2pi Rcosthetacdot RDeltatheta .$$
Now a glance at the "infinitesimal right triangle" with hypotenuse $RDeltatheta$ reveals that the increment of the $z$-coordinate across $A$ amounts to $Delta z=costheta> RDeltatheta$. It follows that in fact
$$ {rm area}(A)=2pi R>Delta z .$$
You can put it this way: The projection of $S^2$ along horizontal rays onto the cylinder touching $S^2$ along the equator is area-preserving.






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    2 Answers
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    A sphere is generated by rotating the right portion of a circle centered at the origin and with radius R about the y-axis, that is, by rotating the curve x=√R^2-y^2 about the y-axis, so the surface area of the required zone would be ∫ (from -c to c) 2π*√R^2-y^2*√R^2/R^2-y^2 dy, now we know that 2c=h( assume that c>0), we got h*∫ 2πR dy=2πRh






    share|cite|improve this answer





















    • Please use MathJax.
      – José Carlos Santos
      Aug 24 '17 at 10:24















    up vote
    0
    down vote













    A sphere is generated by rotating the right portion of a circle centered at the origin and with radius R about the y-axis, that is, by rotating the curve x=√R^2-y^2 about the y-axis, so the surface area of the required zone would be ∫ (from -c to c) 2π*√R^2-y^2*√R^2/R^2-y^2 dy, now we know that 2c=h( assume that c>0), we got h*∫ 2πR dy=2πRh






    share|cite|improve this answer





















    • Please use MathJax.
      – José Carlos Santos
      Aug 24 '17 at 10:24













    up vote
    0
    down vote










    up vote
    0
    down vote









    A sphere is generated by rotating the right portion of a circle centered at the origin and with radius R about the y-axis, that is, by rotating the curve x=√R^2-y^2 about the y-axis, so the surface area of the required zone would be ∫ (from -c to c) 2π*√R^2-y^2*√R^2/R^2-y^2 dy, now we know that 2c=h( assume that c>0), we got h*∫ 2πR dy=2πRh






    share|cite|improve this answer












    A sphere is generated by rotating the right portion of a circle centered at the origin and with radius R about the y-axis, that is, by rotating the curve x=√R^2-y^2 about the y-axis, so the surface area of the required zone would be ∫ (from -c to c) 2π*√R^2-y^2*√R^2/R^2-y^2 dy, now we know that 2c=h( assume that c>0), we got h*∫ 2πR dy=2πRh







    share|cite|improve this answer












    share|cite|improve this answer



    share|cite|improve this answer










    answered Aug 24 '17 at 10:03









    shark

    1




    1












    • Please use MathJax.
      – José Carlos Santos
      Aug 24 '17 at 10:24


















    • Please use MathJax.
      – José Carlos Santos
      Aug 24 '17 at 10:24
















    Please use MathJax.
    – José Carlos Santos
    Aug 24 '17 at 10:24




    Please use MathJax.
    – José Carlos Santos
    Aug 24 '17 at 10:24










    up vote
    0
    down vote













    Consider an "infinitesimal latitude annulus" $A$ of geographical width $Deltatheta$, positioned at the geographical latitude $thetainleft]-{piover2},{piover2}right[$. Its area is given by
    $${rm area}(A)=2pi Rcosthetacdot RDeltatheta .$$
    Now a glance at the "infinitesimal right triangle" with hypotenuse $RDeltatheta$ reveals that the increment of the $z$-coordinate across $A$ amounts to $Delta z=costheta> RDeltatheta$. It follows that in fact
    $$ {rm area}(A)=2pi R>Delta z .$$
    You can put it this way: The projection of $S^2$ along horizontal rays onto the cylinder touching $S^2$ along the equator is area-preserving.






    share|cite|improve this answer

























      up vote
      0
      down vote













      Consider an "infinitesimal latitude annulus" $A$ of geographical width $Deltatheta$, positioned at the geographical latitude $thetainleft]-{piover2},{piover2}right[$. Its area is given by
      $${rm area}(A)=2pi Rcosthetacdot RDeltatheta .$$
      Now a glance at the "infinitesimal right triangle" with hypotenuse $RDeltatheta$ reveals that the increment of the $z$-coordinate across $A$ amounts to $Delta z=costheta> RDeltatheta$. It follows that in fact
      $$ {rm area}(A)=2pi R>Delta z .$$
      You can put it this way: The projection of $S^2$ along horizontal rays onto the cylinder touching $S^2$ along the equator is area-preserving.






      share|cite|improve this answer























        up vote
        0
        down vote










        up vote
        0
        down vote









        Consider an "infinitesimal latitude annulus" $A$ of geographical width $Deltatheta$, positioned at the geographical latitude $thetainleft]-{piover2},{piover2}right[$. Its area is given by
        $${rm area}(A)=2pi Rcosthetacdot RDeltatheta .$$
        Now a glance at the "infinitesimal right triangle" with hypotenuse $RDeltatheta$ reveals that the increment of the $z$-coordinate across $A$ amounts to $Delta z=costheta> RDeltatheta$. It follows that in fact
        $$ {rm area}(A)=2pi R>Delta z .$$
        You can put it this way: The projection of $S^2$ along horizontal rays onto the cylinder touching $S^2$ along the equator is area-preserving.






        share|cite|improve this answer












        Consider an "infinitesimal latitude annulus" $A$ of geographical width $Deltatheta$, positioned at the geographical latitude $thetainleft]-{piover2},{piover2}right[$. Its area is given by
        $${rm area}(A)=2pi Rcosthetacdot RDeltatheta .$$
        Now a glance at the "infinitesimal right triangle" with hypotenuse $RDeltatheta$ reveals that the increment of the $z$-coordinate across $A$ amounts to $Delta z=costheta> RDeltatheta$. It follows that in fact
        $$ {rm area}(A)=2pi R>Delta z .$$
        You can put it this way: The projection of $S^2$ along horizontal rays onto the cylinder touching $S^2$ along the equator is area-preserving.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Aug 24 '17 at 11:39









        Christian Blatter

        170k7111324




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