1. Sep 19, 2005 #1

   Agnostic

   

   
   
   
   ..just wanted to make sure im reading this right..

    

   Agnostic, Sep 19, 2005
2. 
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3. Sep 20, 2005 #2

   TD

   

   Homework Helper

   That is correct.

    

   TD, Sep 20, 2005
4. Sep 20, 2005 #3

   dextercioby

   

   Science Advisor

   Homework Helper

   Insights Author

   Here's the proof
   
   [tex] \tanh ix=\frac{\sinh ix}{\cosh ix}=\frac{i\sin x}{\cos x}=i\tan x [/tex]
   
   Therefore
   
   [tex] ix=\mbox{arc}\tanh \left(i\tan x\right) [/tex]
   
   Pick [itex] x=\arctan y [/itex]
   
   So
   
   [tex] i\arctan y=\mbox{arc}\tanh \left(i\tan\left(\arctan y\right)\right)=\mbox{arc}\tanh iy [/tex]
   
   q.e.d.
   
   Daniel.

    

   dextercioby, Sep 20, 2005

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