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# So... why isn't -1/i = i? watch

1. This is the step that I got wrong which resulted in an integral becoming instead of the correct answer .

I'm doing something stupid aren't I >_>
2. (Original post by wanderlust.xx)
-1/i does = i - who said it doesnt?
3. errrr. it is?
4. -1/i = i
5. No, looks like thats right to me :/

Its just like x/(sqrt x) = sqrt x
6. Your mistake is elsewhere, -1/i=i
7. (Original post by wanderlust.xx)

This is the step that I got wrong which resulted in an integral becoming instead of the correct answer .

I'm doing something stupid aren't I >_>
you are correct.
8. I think your error must lie somewhere else (assuming the question/answer is correct).
9. Right, so can someone clarify something here? I think I've done something wrong... or the lecturer's wrong (which is doubtful, she's quite brilliant).

I'm trying to find the value of where is the unit circle in the complex plane and .

What I see her doing is saying that

according to her.

However, wouldn't the original integral need to be factorised in order to use Cauchy's Integral Formula directly, as follows:

which implies that

... right?

10. (Original post by wanderlust.xx)
Right, so can someone clarify something here? I think I've done something wrong... or the lecturer's wrong (which is doubtful, she's quite brilliant).

I'm trying to find the value of where is the unit circle in the complex plane and .

What I see her doing is saying that

according to her.

However, wouldn't the original integral need to be factorised in order to use Cauchy's Integral Formula directly, as follows:

which implies that

... right?

What on earth have you done on the last line?? The i on the numerator cancels the i in (1/i) - you've just confused yourself by introducing an unnecessary i^2.
11. (Original post by davros)
What on earth have you done on the last line?? The i on the numerator cancels the i in (1/i) - you've just confused yourself by introducing an unnecessary i^2.
Woo minus sign gone awry! Thanks very much.
12. It is.

-1/i * -i/-i = i/-i^2 = i/1 = i

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