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Root mean square help

by coki2000
Tags: root, square
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coki2000
#1
Nov29-09, 08:34 AM
P: 91
Hello,
For 1 and 2 I want to calculate rms then

[tex]x_{rms}=\sqrt{\frac{1}{n}\sum_{i=1}^{n}x_i^2}\Rightarrow x_{1,2}=\sqrt{\frac{1}{2}(1^2+2^2)}=\sqrt{\frac{5}{2}}[/tex]

And also

[tex]x_{rms}=\sqrt{\frac{1}{x_2-x_1}\int_{x_1}^{x_2}f^2(x)dx}[/tex]

For the function [tex]f(x)=x[/tex], [tex]x_1=1[/tex], [tex]x_2=2[/tex]

[tex]x_{rms}=\sqrt{\frac{1}{2-1}\int_{1}^{2}x^2dx}=\sqrt{\frac{7}{3}}[/tex]

Please explain to me where I do wrong.
Thanks
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elibj123
#2
Nov29-09, 01:39 PM
P: 240
You do nothing wrong
Are you expecting to get the same value?
Well you won't because the discrete set {1,2} is different from the continuous set {x | 1<x<2}, therefore you shouldn't get the same value
coki2000
#3
Nov30-09, 05:33 AM
P: 91
Quote Quote by elibj123 View Post
You do nothing wrong
Are you expecting to get the same value?
Well you won't because the discrete set {1,2} is different from the continuous set {x | 1<x<2}, therefore you shouldn't get the same value
Alright how I write this integral form?Thanks.


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