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Thread: Calculating exponential i

  1. #1 Calculating exponential i 
    Forum Junior DivideByZero's Avatar
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    How do you calculate i^i
    or x^i (where x is any number)

    my calculator says i^i = 0.2...
    but what are the calculations behind it?


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  3. #2  
    Forum Professor river_rat's Avatar
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    The problem is that complex logarithms are multivalued functions and thus this exponent does not have one answer (which is actually a blessing and not a curse but that is another story).

    To answer you question, you start off with the euler equation e<sup> i x + 2 pi i n </sup> = cos(x) + i sin(x) for n an integer and find that i = e<sup>i pi /2 (1 + 4 n) </sup>. Your calculator chooses the principle branch of this expression (i.e. n = 0) and to simplfy things i will do the same. So i<sup>i</sup> = (e<sup>i pi/2</sup>)<sup>i</sup> = e<sup> - pi / 2 </sup> which is the answer you got


    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  4. #3  
    Forum Junior DivideByZero's Avatar
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    why is e^(i x + 2 pi i n) = cos(x) + i sin(x) ?
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  5. #4  
    Forum Radioactive Isotope MagiMaster's Avatar
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    Look at the Taylor series for e^x, cos(x) and sin(x).
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