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## Homework Statement

Prove using index notation that,

the x denoting a cross-product.

(

**del**x f

**del**g)=

**del**f x

**del**g

## Homework Equations

## The Attempt at a Solution

d

_{i}f etc. denote partial derivatives.

RHS=e

^{ijk}d

_{j}fd

_{k}g

LHS-I'm not even quite sure how to write it in index notation. Here's my attempt however.

LHS=e

^{ijk}d

_{j}(fd

_{k}g)

But then if I write it like that, I can't tell the difference between LHS and RHS.

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Also can someone check whether the following are correct,

**A.B**=A

_{i}B

^{i}=A

^{i}B

_{i}

(

**A**x

**B**)

_{i}=e

_{ijk}A

_{j}B

_{k}

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