Chapter 8, Problem 21P

In ocean engineering, the equation for a reflected standing wave in a harbor is given by $\lambda =16,t=12,v=48$:

$h=h_0\left[\text{sin}\left(\frac{2\pi x}{\lambda }\right)\text{ cos}\left(\frac{2\pi tv}{\lambda }\right)+e^{-x}\right]$

Solve for the lowest positive value of $x\text{ if }h=0.4h_0$.