The first line of the equation should be
a 1 π ω = ∫ 0 2 π ω ( cos ω t ) f r i c t i o n ( M sin ω t ) d t {\displaystyle a_{1}{\frac {\pi }{\omega }}=\int _{0}^{\frac {2\pi }{\omega }}(\cos \omega t)friction(M\sin \omega t)dt}
Return to errata.
