P. 558, Eq. 11.87

The equation should be

$X_n(x)=c_4[-\frac{\sin \sqrt{{\lambda }_n}L+\sinh \sqrt{{\lambda }_n}L}{\cos \sqrt{{\lambda }_n}L+\cos \sqrt{{\lambda }_n}L}(\cos \sqrt{{\lambda }_n}x-\cosh \sqrt{{\lambda }_n}x)+(\sin \sqrt{{\lambda }_n}x-\sinh \sqrt{{\lambda }_n}x)]$

Return to errata.