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Math Help - root mean square question..

  1. #1
    MHF Contributor
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    root mean square question..

    calculate the RMS (root mean square) of this function.
    http://i50.tinypic.com/2iuq80x.jpg
    the period T=4
    the formula is

    V_{rms}=\sqrt{\frac{1}{T}\int_{0}^{T}V_r^2dt}
    V_{rms}=\frac{1}{4}4 \int_{0}^{T}(4t)^2 dt
    i get a latex error here the code is:
    V_{rms}=\frac{1}{4}4\int_{0}^{T}(4t)^2dt}

    V_rms=\sqrt{s}=\sqrt{\frac{16}{3}}
    the solution says that they divide the graph into 4 triangles
    and they sum their areas

    but they dont use the integral?
    why they say (4t)^2
    from where the 4t comes from?

    why they say that its the root of the area
    why they dont divide by the period?
    Last edited by CaptainBlack; January 24th 2010 at 02:31 AM.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by transgalactic View Post
    calculate the RMS (root mean square) of this function.
    http://i50.tinypic.com/2iuq80x.jpg
    the period T=4
    the formula is

    V_{rms}=\sqrt{\frac{1}{T}\int_{0}^{T}V_r^2dt}
    V_{rms}=\frac{1}{4}4 \int_{0}^{T}(4t)^2 dt
    i get a latex error here the code is:
    V_{rms}=\frac{1}{4}4\int_{0}^{T}(4t)^2dt}
    How do you get that last expression from the definition of RMS value on the line above?

    Compute the mean square first (which is what is under the square root sign in the definition of RMS value).

    You do the integral by splitting it into well behaved pieces (that looks like three pieces to me)

    CB
    Last edited by CaptainBlack; January 24th 2010 at 03:19 AM.
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