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Math Help - [SOLVED] complex numbers amplitude and phase - complex amplitude?

  1. #1
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    [SOLVED] complex numbers amplitude and phase - complex amplitude?

    I have a problem

    find the amplitude and plot the phase of the complex number

    j e^{(1+j)\pi t}

    I have an exam tomorrow and this may come up not sure where to start, its basically the j at the start that is throwing me off, as i did not think it was possible to have a complex amplitude since it should be square root of the modulus.

    thanks in advance for help
    Last edited by mr fantastic; January 19th 2009 at 12:22 PM. Reason: Fixed the latex
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  2. #2
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    Quote Originally Posted by checkthiskid View Post
    I have a problem

    find the amplitude and plot the phase of the complex number

    je^{(1+j)\pi t}

    I have an exam tomorrow and this may come up not sure where to start, its basically the j at the start that is throwing me off, as i did not think it was possible to have a complex amplitude since it should be square root of the modulus.

    thanks in advance for help
    Note that j = e^{j \pi/2}.
    Last edited by mr fantastic; January 19th 2009 at 01:59 PM. Reason: Fixed the latex in the quote too.
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  3. #3
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    thanks seems kinda obvious when you say that
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    actually iv ended up with

    e^{j(\pi/2 + \pi t)+ \pi t}

    that means part of the phase is not a multiple of j that cant be right?

    (sorry dnt know how to use that equation tool)


    or does that mean that the amplitude varies with t? with an amplitude of e^{\pi t}
    Last edited by mr fantastic; January 19th 2009 at 02:01 PM. Reason: Fixed latex, merged posts
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  5. #5
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    Quote Originally Posted by checkthiskid View Post
    actually iv ended up with

    e^{j(\pi/2 + \pi t)+ \pi t}

    that means part of the phase is not a multiple of j that cant be right?

    (sorry dnt know how to use that equation tool)


    or does that mean that the amplitude varies with t? with an amplitude of e^{\pi t}
    e^{j(\pi/2 + \pi t)+ \pi t} = e^{\pi t} \cdot e^{j (\pi/2 + \pi t)} .

    The amplitude is e^{\pi t} and the phase (argument) is \frac{\pi}{2} + \pi t.
    Last edited by mr fantastic; January 19th 2009 at 02:20 PM. Reason: Fixed a careless mistake
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  6. #6
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    Shouldn't the argument be  \frac{\pi}{2}+\pi t ?
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  7. #7
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    Quote Originally Posted by chiph588@ View Post
    Shouldn't the argument be  \frac{\pi}{2}+\pi t ?
    yeah got it now thanks
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