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Euler's formula question

  1. Nov 10, 2012 #1
    If e^iPi/2=i, what does e^-iPi/2 equal? And could you please write it out in cos + sin notation? For some reason I am not geting this. This is not homework, by the way, its come up in an article on spinors I'm reading Thanks.
  2. jcsd
  3. Nov 10, 2012 #2
    A simple google check would do the trick.

    Anywho, e^(ix)=cos(x)+i*sin(x) for complex variable x.
  4. Nov 10, 2012 #3
    Continuing with this. If [itex]x=-\pi /2[/itex], then

    [tex]e^{-i\pi /2}=\cos(-\pi/2)+i\sin(-\pi/2)=-i.[/tex]
  5. Nov 10, 2012 #4
    I got the first one Klungo. Thanks for the follow up micromass. Now I got it, its just like spinning the dial from the top of the complex plane to the bottom.
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