実効値は以下のようになる。
\begin{eqnarray}
|f(x)| &=& \frac{4}{\pi}\sqrt{\left(\frac{1}{2}\right)^{2}
+\left(\frac{1}{3\sqrt{2}}\right)^{2}+
\left(\frac{1}{15\sqrt{2}}\right)^{2}}\nonumber\\
&=&
\frac{4}{\pi}\sqrt{
\frac{1}{4}+\frac{1}{18}+\frac{1}{450}}\nonumber\\
&=&
\sqrt{
\frac{16}{\pi^{2}}\frac{1}{4}+\frac{16}{\pi^{2}}\frac{1}{18}+\frac{16}{\pi^{2}}\frac{1}{450}}\nonumber\\
&=&
\underline{ \sqrt{
\frac{4}{\pi^{2}}+\frac{8}{9\pi^{2}}+\frac{8}{225\pi^{2}}}}
\end{eqnarray}
