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avatar+9676 

So according to W/A, you can take the natural logarithm of i to get i*pi/2 but how do you get the answer?

So the questions is: Prove \(\ln(\sqrt{-1})=\dfrac{\sqrt{-\pi^2}}{2}\) I turned all the 'i's into sqrt(-1).

 Sep 29, 2016
edited by MaxWong  Sep 29, 2016

Best Answer 

 #3
avatar+118723 
+5

Yes that is another valid proof but it would still be polite to recognise the valid proof that I had already given you.

 Sep 29, 2016
 #1
avatar+118723 
+5

How about this :/

 

 

\(let\\ \begin{align} x&=ln\; i\\ e^x&=i\\now\\ i&=cos\frac{\pi}{2}+isin\frac{\pi}{2}\\\therefore\\ i&=e^{(\pi/2)i}\\\therefore \\ e^x&=e^{(\pi/2)i}\\\therefore\\ x&=\frac{\pi }{2}\;i \\\therefore\\ ln\;i&=\frac{\sqrt{-\pi^2}}{2} \end{align} \)

 Sep 29, 2016
 #2
avatar+9676 
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I just came up with a proof. Apologies to everyone.

\(\ln(\sqrt{-1})=\dfrac{\ln(-1)}{2}\\ e^{i\pi}+1=0\\ e^{i\pi}=-1\\ i\pi = \ln(-1)\\ \therefore \ln(\sqrt{-1})=\dfrac{\ln(-1)}{2}=\dfrac{i\pi}{2}\)

 Sep 29, 2016
 #3
avatar+118723 
+5
Best Answer

Yes that is another valid proof but it would still be polite to recognise the valid proof that I had already given you.

Melody Sep 29, 2016

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