# Root mean square help

by coki2000
Tags: root, square
 P: 91 Hello, For 1 and 2 I want to calculate rms then $$x_{rms}=\sqrt{\frac{1}{n}\sum_{i=1}^{n}x_i^2}\Rightarrow x_{1,2}=\sqrt{\frac{1}{2}(1^2+2^2)}=\sqrt{\frac{5}{2}}$$ And also $$x_{rms}=\sqrt{\frac{1}{x_2-x_1}\int_{x_1}^{x_2}f^2(x)dx}$$ For the function $$f(x)=x$$, $$x_1=1$$, $$x_2=2$$ $$x_{rms}=\sqrt{\frac{1}{2-1}\int_{1}^{2}x^2dx}=\sqrt{\frac{7}{3}}$$ Please explain to me where I do wrong. Thanks