Figure 3.1.8(a) animates the passage of the cutting plane $x\=c$ through the surface $z\=f\left(x\,y\right)$ defined implicitly by the equation
$xy\+z\cosh \left(z-1\right)\=1$.

The animation is constructed from coding primitives because the CrossSection command (and its companion tutor) will not accept an implicitly defined surface.

Indeed, Figure 3.1.8(a) is built with the intersectplot command, which works numerically to determine the intersection of the plane $x\=c$ with the implicitly given surface.

Maple can, however, represent $z\left(x\,y\right)$ in terms of its RootOf structure, and the spacecurve command will then calculate and draw the intersection with the plane $x\=c$.