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Mean and RMS

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  • 11-10-2015 11:00am
    #1
    Hedgecutter
    Registered Users Posts: 1,030 ✭✭✭


    Can't understand where I have gone wrong on these two. Answer from the book are miles from mine.


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    #2
    Hedgecutter
    Registered Users Posts: 1,030 ✭✭✭Hedgecutter


    RMS


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    #3
    Hedgecutter
    Registered Users Posts: 1,030 ✭✭✭Hedgecutter


    Mean value


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    #4
    TheBody
    Registered Users Posts: 5,619 ✭✭✭TheBody


    The first thing I have to say is that I know nothing about the rms and the mean formulae. I am presuming that your first lines are correct.

    With regards the rms, your formula says to square everything. It looks like you forgot to square the 25 in your first line in blue.

    With regards the mean, when you are putting in the limits of integration, you said that the [latex]-\frac{1}{100\pi}\cos(100 \pi (0))=0[/latex]. That is not true. It is [latex]-\frac{1}{100\pi}[/latex].

    Pretty good effort all in all.


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    #5
    MathsManiac
    Registered Users Posts: 1,595 ✭✭✭MathsManiac


    Just as TheBody pointed out that cos(0) = 1, so too you should note that cos(1000*Pi) is also 1, so the overall expression yields 0.

    By the way, where did you get the 0.0795 - it seems like 1/(4*Pi), which would not be correct anyway...


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