code class$=$"asciimath"$>$A water wave traveling in a straight line on a lake is described by the equation y$($x$,$t$)=(2\mathrm{.}75$cm$)$cos$(0\mathrm{.}410$ra$($d$)/($c$)$mx$+6\mathrm{.}20$ra$($d$)/($s$)$t$)$ where y is the displacement perpendicular to the undisturbed surface of the lake.