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Surface area of a sphere over a disc


Compute the surface area of an oblate paraboloidFinding the sphere surface area using the divergence theorem and sphere volumeWhy does the integral of the surface area of a sphere equal its volume?Calculate surface area of a sphere using the surface integralCalculating surface areaLine integrals - Surface areaSurface integral of function over intersection between plane and unit sphereIntegration over sphere area elementsHow to prove that $text{area}( S_r(x) cap B_R(0)) leq text{area}(S_R(0))$?Volume between cone and sphere of radius $sqrt2$ with surface integral













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What's the surface area of the sphere $x^2 + y^2 + z^2 = 1$ over the disc $(x-1/2)^2 + y^2 le 1/4$ ?



I've tried something, but I don't think it's right, as it's not a "nice answer"



So here is what I've done:



Firstly I parameterized using $x = r cos(t)$, $y= r sin(t)$, $z=z$.



$$dS = sqrt{1+(dz/dx)^2+(dz/dy)^2} dA$$



$$dz/dx=2x , dz/dy=2y $$



Which gives me $$ sqrt{1+4x^2+4y^2} dA = sqrt{1+4r^2} r dr dt$$



Integral then becomes:
S = $int_0^{2pi} int_0^{1/2}sqrt{1+4r^2} r dr dt$



Solving this gives me the result $=0,96$, however I don't think it's right










share|cite|improve this question











$endgroup$












  • $begingroup$
    Please use MathJax to format posts on this site.
    $endgroup$
    – saulspatz
    yesterday










  • $begingroup$
    I am sorry, last time it made changes by itself, will try to sort it out asap
    $endgroup$
    – LostCoder
    yesterday










  • $begingroup$
    I made some edits to get you started
    $endgroup$
    – saulspatz
    yesterday










  • $begingroup$
    Thank you very much! :)
    $endgroup$
    – LostCoder
    yesterday










  • $begingroup$
    You are integrating over the disk $x^2y^2leqfrac14$ which is not the region specified in the problem
    $endgroup$
    – saulspatz
    yesterday
















0












$begingroup$


What's the surface area of the sphere $x^2 + y^2 + z^2 = 1$ over the disc $(x-1/2)^2 + y^2 le 1/4$ ?



I've tried something, but I don't think it's right, as it's not a "nice answer"



So here is what I've done:



Firstly I parameterized using $x = r cos(t)$, $y= r sin(t)$, $z=z$.



$$dS = sqrt{1+(dz/dx)^2+(dz/dy)^2} dA$$



$$dz/dx=2x , dz/dy=2y $$



Which gives me $$ sqrt{1+4x^2+4y^2} dA = sqrt{1+4r^2} r dr dt$$



Integral then becomes:
S = $int_0^{2pi} int_0^{1/2}sqrt{1+4r^2} r dr dt$



Solving this gives me the result $=0,96$, however I don't think it's right










share|cite|improve this question











$endgroup$












  • $begingroup$
    Please use MathJax to format posts on this site.
    $endgroup$
    – saulspatz
    yesterday










  • $begingroup$
    I am sorry, last time it made changes by itself, will try to sort it out asap
    $endgroup$
    – LostCoder
    yesterday










  • $begingroup$
    I made some edits to get you started
    $endgroup$
    – saulspatz
    yesterday










  • $begingroup$
    Thank you very much! :)
    $endgroup$
    – LostCoder
    yesterday










  • $begingroup$
    You are integrating over the disk $x^2y^2leqfrac14$ which is not the region specified in the problem
    $endgroup$
    – saulspatz
    yesterday














0












0








0





$begingroup$


What's the surface area of the sphere $x^2 + y^2 + z^2 = 1$ over the disc $(x-1/2)^2 + y^2 le 1/4$ ?



I've tried something, but I don't think it's right, as it's not a "nice answer"



So here is what I've done:



Firstly I parameterized using $x = r cos(t)$, $y= r sin(t)$, $z=z$.



$$dS = sqrt{1+(dz/dx)^2+(dz/dy)^2} dA$$



$$dz/dx=2x , dz/dy=2y $$



Which gives me $$ sqrt{1+4x^2+4y^2} dA = sqrt{1+4r^2} r dr dt$$



Integral then becomes:
S = $int_0^{2pi} int_0^{1/2}sqrt{1+4r^2} r dr dt$



Solving this gives me the result $=0,96$, however I don't think it's right










share|cite|improve this question











$endgroup$




What's the surface area of the sphere $x^2 + y^2 + z^2 = 1$ over the disc $(x-1/2)^2 + y^2 le 1/4$ ?



I've tried something, but I don't think it's right, as it's not a "nice answer"



So here is what I've done:



Firstly I parameterized using $x = r cos(t)$, $y= r sin(t)$, $z=z$.



$$dS = sqrt{1+(dz/dx)^2+(dz/dy)^2} dA$$



$$dz/dx=2x , dz/dy=2y $$



Which gives me $$ sqrt{1+4x^2+4y^2} dA = sqrt{1+4r^2} r dr dt$$



Integral then becomes:
S = $int_0^{2pi} int_0^{1/2}sqrt{1+4r^2} r dr dt$



Solving this gives me the result $=0,96$, however I don't think it's right







multivariable-calculus area applications multiple-integral






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited yesterday







LostCoder

















asked yesterday









LostCoderLostCoder

115




115












  • $begingroup$
    Please use MathJax to format posts on this site.
    $endgroup$
    – saulspatz
    yesterday










  • $begingroup$
    I am sorry, last time it made changes by itself, will try to sort it out asap
    $endgroup$
    – LostCoder
    yesterday










  • $begingroup$
    I made some edits to get you started
    $endgroup$
    – saulspatz
    yesterday










  • $begingroup$
    Thank you very much! :)
    $endgroup$
    – LostCoder
    yesterday










  • $begingroup$
    You are integrating over the disk $x^2y^2leqfrac14$ which is not the region specified in the problem
    $endgroup$
    – saulspatz
    yesterday


















  • $begingroup$
    Please use MathJax to format posts on this site.
    $endgroup$
    – saulspatz
    yesterday










  • $begingroup$
    I am sorry, last time it made changes by itself, will try to sort it out asap
    $endgroup$
    – LostCoder
    yesterday










  • $begingroup$
    I made some edits to get you started
    $endgroup$
    – saulspatz
    yesterday










  • $begingroup$
    Thank you very much! :)
    $endgroup$
    – LostCoder
    yesterday










  • $begingroup$
    You are integrating over the disk $x^2y^2leqfrac14$ which is not the region specified in the problem
    $endgroup$
    – saulspatz
    yesterday
















$begingroup$
Please use MathJax to format posts on this site.
$endgroup$
– saulspatz
yesterday




$begingroup$
Please use MathJax to format posts on this site.
$endgroup$
– saulspatz
yesterday












$begingroup$
I am sorry, last time it made changes by itself, will try to sort it out asap
$endgroup$
– LostCoder
yesterday




$begingroup$
I am sorry, last time it made changes by itself, will try to sort it out asap
$endgroup$
– LostCoder
yesterday












$begingroup$
I made some edits to get you started
$endgroup$
– saulspatz
yesterday




$begingroup$
I made some edits to get you started
$endgroup$
– saulspatz
yesterday












$begingroup$
Thank you very much! :)
$endgroup$
– LostCoder
yesterday




$begingroup$
Thank you very much! :)
$endgroup$
– LostCoder
yesterday












$begingroup$
You are integrating over the disk $x^2y^2leqfrac14$ which is not the region specified in the problem
$endgroup$
– saulspatz
yesterday




$begingroup$
You are integrating over the disk $x^2y^2leqfrac14$ which is not the region specified in the problem
$endgroup$
– saulspatz
yesterday










1 Answer
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$begingroup$

The border of the region in polar coordinates is:
$$(rcostheta - 1/2)^2 + (rsintheta)^2 = 1/4,$$
$$r = costheta,$$
with $thetaincdots$ (Draw the circle to see the interval of variation of $theta$).






share|cite|improve this answer









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    1 Answer
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    oldest

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    oldest

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    0












    $begingroup$

    The border of the region in polar coordinates is:
    $$(rcostheta - 1/2)^2 + (rsintheta)^2 = 1/4,$$
    $$r = costheta,$$
    with $thetaincdots$ (Draw the circle to see the interval of variation of $theta$).






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      The border of the region in polar coordinates is:
      $$(rcostheta - 1/2)^2 + (rsintheta)^2 = 1/4,$$
      $$r = costheta,$$
      with $thetaincdots$ (Draw the circle to see the interval of variation of $theta$).






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        The border of the region in polar coordinates is:
        $$(rcostheta - 1/2)^2 + (rsintheta)^2 = 1/4,$$
        $$r = costheta,$$
        with $thetaincdots$ (Draw the circle to see the interval of variation of $theta$).






        share|cite|improve this answer









        $endgroup$



        The border of the region in polar coordinates is:
        $$(rcostheta - 1/2)^2 + (rsintheta)^2 = 1/4,$$
        $$r = costheta,$$
        with $thetaincdots$ (Draw the circle to see the interval of variation of $theta$).







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered 19 hours ago









        Martín-Blas Pérez PinillaMartín-Blas Pérez Pinilla

        34.5k42971




        34.5k42971






























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