Calculating Vrms: Homework Equations & Solutions Explained

[kostoglotov]

Homework Statement

imgur link: https://i.imgur.com/9jozS67.png

Homework Equations

The Attempt at a Solution

[/B]
Shouldn't I use $V_{rms} = \sqrt{\frac{1}{T}\int_T v^2 dt}$?

Which would be

$$\sqrt{\frac{100}{2\pi}\int_0^{2\pi/100}(20+60cos(100t))^2dt}$$

This equals $\approx 79.88 V$

The answer is given as $\approx 46.9V$ and the solution manual shows the following working

$$\sqrt{20^2 + \frac{60^2}{2}}$$

Why do they apply that solution and not the one I used?

 

[gneill]

You might want to check your integration. I find that the integral matches the manual's result.