Evaluating Double Integral












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Evaluate $$iint_{S} (x^3+y^3),dy,dz + (z^3+y^3),dz,dx + (x^3+z^3),dx,dy$$ where $S$ is the surface of the sphere $x^2+y^2+z^2= a^2$.




Spherical coordinates help me in this question, $r^2=a^2$.



We can also write $$iiint_{S} 2(x^3+y^3+z^3),dx,dy,dz$$ or not?



Thank you for your advanced ideas.










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    $begingroup$



    Evaluate $$iint_{S} (x^3+y^3),dy,dz + (z^3+y^3),dz,dx + (x^3+z^3),dx,dy$$ where $S$ is the surface of the sphere $x^2+y^2+z^2= a^2$.




    Spherical coordinates help me in this question, $r^2=a^2$.



    We can also write $$iiint_{S} 2(x^3+y^3+z^3),dx,dy,dz$$ or not?



    Thank you for your advanced ideas.










    share|cite|improve this question











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      0












      0








      0


      1



      $begingroup$



      Evaluate $$iint_{S} (x^3+y^3),dy,dz + (z^3+y^3),dz,dx + (x^3+z^3),dx,dy$$ where $S$ is the surface of the sphere $x^2+y^2+z^2= a^2$.




      Spherical coordinates help me in this question, $r^2=a^2$.



      We can also write $$iiint_{S} 2(x^3+y^3+z^3),dx,dy,dz$$ or not?



      Thank you for your advanced ideas.










      share|cite|improve this question











      $endgroup$





      Evaluate $$iint_{S} (x^3+y^3),dy,dz + (z^3+y^3),dz,dx + (x^3+z^3),dx,dy$$ where $S$ is the surface of the sphere $x^2+y^2+z^2= a^2$.




      Spherical coordinates help me in this question, $r^2=a^2$.



      We can also write $$iiint_{S} 2(x^3+y^3+z^3),dx,dy,dz$$ or not?



      Thank you for your advanced ideas.







      calculus integration indefinite-integrals






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      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Mar 19 at 23:41









      Robert Howard

      2,3033935




      2,3033935










      asked Feb 1 at 8:58









      mathsstudentmathsstudent

      536




      536






















          1 Answer
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          $begingroup$

          Based on Mikhail Ostrogradsky a surface integral can be converted to volume integral where P, Q, R are function of x, y, z.



          $$iint_SPmathop{dy}mathop{dz} + Qmathop{dz}mathop{dx} + Rmathop{dx}mathop{dy} = iiint_V(frac{partial P}{partial x} + frac{partial Q}{partial y} + frac{partial R}{partial z})mathop{dx}mathop{dy}mathop{dz}$$



          Hence the surface integral becomes



          $$iiint_V(3x^2 + 3y^2 + 3z^2)dxmathop{dy}mathop{dz}$$
          $$= 3iiint_V r^2mathop{dx}mathop{dy}mathop{dz}$$
          $$= 3int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}}int_{0}^{2pi} r^4cosphi mathop{dtheta}mathop{dphi}mathop{dr}$$
          $$= 6pi int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}} r^4cosphi mathop{dphi}mathop{dr}$$
          $$= 12pi int_{0}^{a} r^4 mathop{dr}$$
          $$= frac{12}{5}pi a^5$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            You are right. I am making an edit. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 21:35










          • $begingroup$
            Note you can use iint_S $iint_S$ and iiint_V $iiint_V$ for multidimensional integrals, it renders better than succession of intint $intint$
            $endgroup$
            – zwim
            Mar 19 at 22:17










          • $begingroup$
            This is good to know. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 22:19










          • $begingroup$
            +1 For Ostrogradsky :).
            $endgroup$
            – MachineLearner
            Mar 19 at 23:52












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          1 Answer
          1






          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          3












          $begingroup$

          Based on Mikhail Ostrogradsky a surface integral can be converted to volume integral where P, Q, R are function of x, y, z.



          $$iint_SPmathop{dy}mathop{dz} + Qmathop{dz}mathop{dx} + Rmathop{dx}mathop{dy} = iiint_V(frac{partial P}{partial x} + frac{partial Q}{partial y} + frac{partial R}{partial z})mathop{dx}mathop{dy}mathop{dz}$$



          Hence the surface integral becomes



          $$iiint_V(3x^2 + 3y^2 + 3z^2)dxmathop{dy}mathop{dz}$$
          $$= 3iiint_V r^2mathop{dx}mathop{dy}mathop{dz}$$
          $$= 3int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}}int_{0}^{2pi} r^4cosphi mathop{dtheta}mathop{dphi}mathop{dr}$$
          $$= 6pi int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}} r^4cosphi mathop{dphi}mathop{dr}$$
          $$= 12pi int_{0}^{a} r^4 mathop{dr}$$
          $$= frac{12}{5}pi a^5$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            You are right. I am making an edit. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 21:35










          • $begingroup$
            Note you can use iint_S $iint_S$ and iiint_V $iiint_V$ for multidimensional integrals, it renders better than succession of intint $intint$
            $endgroup$
            – zwim
            Mar 19 at 22:17










          • $begingroup$
            This is good to know. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 22:19










          • $begingroup$
            +1 For Ostrogradsky :).
            $endgroup$
            – MachineLearner
            Mar 19 at 23:52
















          3












          $begingroup$

          Based on Mikhail Ostrogradsky a surface integral can be converted to volume integral where P, Q, R are function of x, y, z.



          $$iint_SPmathop{dy}mathop{dz} + Qmathop{dz}mathop{dx} + Rmathop{dx}mathop{dy} = iiint_V(frac{partial P}{partial x} + frac{partial Q}{partial y} + frac{partial R}{partial z})mathop{dx}mathop{dy}mathop{dz}$$



          Hence the surface integral becomes



          $$iiint_V(3x^2 + 3y^2 + 3z^2)dxmathop{dy}mathop{dz}$$
          $$= 3iiint_V r^2mathop{dx}mathop{dy}mathop{dz}$$
          $$= 3int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}}int_{0}^{2pi} r^4cosphi mathop{dtheta}mathop{dphi}mathop{dr}$$
          $$= 6pi int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}} r^4cosphi mathop{dphi}mathop{dr}$$
          $$= 12pi int_{0}^{a} r^4 mathop{dr}$$
          $$= frac{12}{5}pi a^5$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            You are right. I am making an edit. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 21:35










          • $begingroup$
            Note you can use iint_S $iint_S$ and iiint_V $iiint_V$ for multidimensional integrals, it renders better than succession of intint $intint$
            $endgroup$
            – zwim
            Mar 19 at 22:17










          • $begingroup$
            This is good to know. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 22:19










          • $begingroup$
            +1 For Ostrogradsky :).
            $endgroup$
            – MachineLearner
            Mar 19 at 23:52














          3












          3








          3





          $begingroup$

          Based on Mikhail Ostrogradsky a surface integral can be converted to volume integral where P, Q, R are function of x, y, z.



          $$iint_SPmathop{dy}mathop{dz} + Qmathop{dz}mathop{dx} + Rmathop{dx}mathop{dy} = iiint_V(frac{partial P}{partial x} + frac{partial Q}{partial y} + frac{partial R}{partial z})mathop{dx}mathop{dy}mathop{dz}$$



          Hence the surface integral becomes



          $$iiint_V(3x^2 + 3y^2 + 3z^2)dxmathop{dy}mathop{dz}$$
          $$= 3iiint_V r^2mathop{dx}mathop{dy}mathop{dz}$$
          $$= 3int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}}int_{0}^{2pi} r^4cosphi mathop{dtheta}mathop{dphi}mathop{dr}$$
          $$= 6pi int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}} r^4cosphi mathop{dphi}mathop{dr}$$
          $$= 12pi int_{0}^{a} r^4 mathop{dr}$$
          $$= frac{12}{5}pi a^5$$






          share|cite|improve this answer











          $endgroup$



          Based on Mikhail Ostrogradsky a surface integral can be converted to volume integral where P, Q, R are function of x, y, z.



          $$iint_SPmathop{dy}mathop{dz} + Qmathop{dz}mathop{dx} + Rmathop{dx}mathop{dy} = iiint_V(frac{partial P}{partial x} + frac{partial Q}{partial y} + frac{partial R}{partial z})mathop{dx}mathop{dy}mathop{dz}$$



          Hence the surface integral becomes



          $$iiint_V(3x^2 + 3y^2 + 3z^2)dxmathop{dy}mathop{dz}$$
          $$= 3iiint_V r^2mathop{dx}mathop{dy}mathop{dz}$$
          $$= 3int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}}int_{0}^{2pi} r^4cosphi mathop{dtheta}mathop{dphi}mathop{dr}$$
          $$= 6pi int_{0}^{a}int_{-frac{pi}{2}}^{frac{pi}{2}} r^4cosphi mathop{dphi}mathop{dr}$$
          $$= 12pi int_{0}^{a} r^4 mathop{dr}$$
          $$= frac{12}{5}pi a^5$$







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Mar 19 at 22:22









          zwim

          12.7k832




          12.7k832










          answered Mar 19 at 20:42









          KY TangKY Tang

          50436




          50436












          • $begingroup$
            You are right. I am making an edit. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 21:35










          • $begingroup$
            Note you can use iint_S $iint_S$ and iiint_V $iiint_V$ for multidimensional integrals, it renders better than succession of intint $intint$
            $endgroup$
            – zwim
            Mar 19 at 22:17










          • $begingroup$
            This is good to know. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 22:19










          • $begingroup$
            +1 For Ostrogradsky :).
            $endgroup$
            – MachineLearner
            Mar 19 at 23:52


















          • $begingroup$
            You are right. I am making an edit. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 21:35










          • $begingroup$
            Note you can use iint_S $iint_S$ and iiint_V $iiint_V$ for multidimensional integrals, it renders better than succession of intint $intint$
            $endgroup$
            – zwim
            Mar 19 at 22:17










          • $begingroup$
            This is good to know. Thanks.
            $endgroup$
            – KY Tang
            Mar 19 at 22:19










          • $begingroup$
            +1 For Ostrogradsky :).
            $endgroup$
            – MachineLearner
            Mar 19 at 23:52
















          $begingroup$
          You are right. I am making an edit. Thanks.
          $endgroup$
          – KY Tang
          Mar 19 at 21:35




          $begingroup$
          You are right. I am making an edit. Thanks.
          $endgroup$
          – KY Tang
          Mar 19 at 21:35












          $begingroup$
          Note you can use iint_S $iint_S$ and iiint_V $iiint_V$ for multidimensional integrals, it renders better than succession of intint $intint$
          $endgroup$
          – zwim
          Mar 19 at 22:17




          $begingroup$
          Note you can use iint_S $iint_S$ and iiint_V $iiint_V$ for multidimensional integrals, it renders better than succession of intint $intint$
          $endgroup$
          – zwim
          Mar 19 at 22:17












          $begingroup$
          This is good to know. Thanks.
          $endgroup$
          – KY Tang
          Mar 19 at 22:19




          $begingroup$
          This is good to know. Thanks.
          $endgroup$
          – KY Tang
          Mar 19 at 22:19












          $begingroup$
          +1 For Ostrogradsky :).
          $endgroup$
          – MachineLearner
          Mar 19 at 23:52




          $begingroup$
          +1 For Ostrogradsky :).
          $endgroup$
          – MachineLearner
          Mar 19 at 23:52


















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