What is x^i? How can you rewrite it?

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Discussion Overview

The discussion centers around the expression x^i, exploring its meaning and representation, particularly in the context of complex numbers and the complex plane. Participants examine the implications of this expression and its graphical representation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions the meaning of x^i and notes that (x^i)^i = 1/x, expressing confusion about its implications.
  • Another participant suggests that viewing x^i in the complex plane provides clarity, explaining that x^i can be expressed as e^{i ln(x)}, indicating a rotation in the complex plane.
  • It is mentioned that Wolfram Alpha calculates 3^i to be approximately 0.455 + 0.890i, prompting curiosity about the calculation method.
  • A participant elaborates that the real part of x^i corresponds to cos(ln(x)) and the imaginary part to sin(ln(x)).
  • One participant expresses appreciation for the clarity gained from the discussion, noting the beauty of the graph related to the real and imaginary parts of x^i.
  • Another participant comments on the simplicity gained from understanding rotations in the context of phasors and mentions a resource that discusses imaginary exponents and their applications in electronics and wave analysis.

Areas of Agreement / Disagreement

The discussion reflects a general agreement on the interpretation of x^i as a rotation in the complex plane, but it does not resolve all questions regarding its implications or the methods of calculation.

Contextual Notes

Participants do not fully explore the assumptions behind the calculations or the definitions of the functions involved, leaving some aspects of the discussion open to interpretation.

Who May Find This Useful

This discussion may be of interest to those studying complex numbers, mathematical analysis, or applications in physics and engineering, particularly in relation to wave phenomena and electrical engineering.

nhmllr
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Very simple question... What is x^i? How can you rewrite it?
All I could figure out is that (x^i)^i = 1/x, but that doesn't help much
Wolfram Alpha gave me this graph (real part in blue, imaginary in orange)
http://www4c.wolframalpha.com/Calculate/MSP/MSP17119i95eid65h0gce900001e7b96h101dd87d6?MSPStoreType=image/gif&s=62&w=320&h=119&cdf=RangeControl
Which is a very strange graph.

What happens?
 
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It is probably clearer if you look at it in the complex plane.
Apart from that, what happens is exactly what the graph says happens.

consider:
e^{i\theta} is just the unit vector rotated anti-clockwise in the complex plane by \theta radiens.

a^b = e^{b\ln{a}} so x^i = e^{i\ln{x}} so x^i is the unit vector rotated by ln(x) radiens in the complex plane.
 
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Simon Bridge said:
It is probably clearer if you look at it in the complex plane.
Apart from that, what happens is exactly what the graph says happens.

Okay, so wolfram alpha says that 3^i is about 0.455 + 0.890i
How did it figure that out?
 


Ah - you posted while I edited: that's a bad habit of mine.
It's a rotation in the complex plane.
The real part is the cos(ln(x)) and the imaginary part is sin(ln(x))
 
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That made so much more sense than I expected it to.
It also explains this graph of y=Re(x^i)^2+Im(x^i)^2
http://www4b.wolframalpha.com/Calculate/MSP/MSP237219i95h4480ahf33i00001h6c277de8811fe7?MSPStoreType=image/gif&s=34&w=307&h=136&cdf=RangeControl
Friggin' beautiful.
 
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Yep - when you get used to rotating phasors lots of things get simple.
I dredged up a link for you. It covers the whole imaginary exponent thing (like what happens when you raise a complex number to the power of another complex number) then links to a bunch of applications.

It's also used in analyzing linear networks (electronics) and anything with waves.
 

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