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Prove the identity [tex]\int_{\partial D}\phi \nabla \phi \cdot \n \ds = \int \int_{D} (\phi \nabla^2 \phi + \nabla \phi \cdot \nabla \phi) \dA [/tex]

Can I just let [tex]\phi[/tex] be equal to P + Q, substitute into the left side, and try to derive the right side? This is a weird looking identity by the way.

Can I just let [tex]\phi[/tex] be equal to P + Q, substitute into the left side, and try to derive the right side? This is a weird looking identity by the way.

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