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We know that A x (BxC)= (A·C)B-(A·B)C (*)

In the following example, we can treat ∇ as a vector and apply the formula (*) above to get the correct answer

∇x(∇xV)= ∇(∇·V)-∇^2 V

But in this example, the formula (*) seems to fail

∇x(UxV)≠U(∇·V)-V(∇·U)

Why?

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# Question about del

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