# Math Help - root mean square question..

1. ## 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?

2. Originally Posted by transgalactic
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