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Suffix notation problem watch

1. Hi there. A bit unsure with a question.

Use suffix notation to write as a simpler vector expression (involving no cross products).

I'll put what I've done.

And:

So I get

for the first expression, and

for the second.

So second subtracted from first gives

I can't help but feel the answer should be 0 (or something simpler). Can anyone see any mistakes?
2. (Original post by Goliathmo)
Hi there. A bit unsure with a question.

Use suffix notation to write as a simpler vector expression (involving no cross products).

I'll put what I've done.

And:

So I get

for the first expression, and

for the second.

So second subtracted from first gives

I can't help but feel the answer should be 0 (or something simpler). Can anyone see any mistakes?
That last expression looks relatively simple to me. Try writing it out as a vector expression.
3. Looking only at your final answer, remember that using suffix notation, repeated indices are summed over. Think about a_m*c_m in the first term for instance.
4. (Original post by Slumpy)
Looking only at your final answer, remember that using suffix notation, repeated indices are summed over. Think about a_m*c_m in the first term for instance.
Ok. So we get?

5. That's correct.
6. (Original post by Slumpy)
That's correct.
Then I've made a mistake somewhere, because that isn't equivalent to the expression I was trying to simplify.
7. **** I think I know where I went wrong, I didn't consider the order of the vector product in the second expression.

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