Drag on the graph to rotate it.

The definitions of x(u,v), y(u,v),
and z(u,v) can use: the variables *u* and *v*; the operators +, −, `*`

,
and `/`

; the functions *sin*(*x*), *cos*(*x*), *atan*(*x*),
*abs*(*x*), *exp*(*x*), *log*(*x*), and *pow*(*x,y*); and
the constant *pi*. Note that there is no exponential operator, but *pow*(*x,y*)
does exponentiation. Angles are measured in radians. The *scale* determines the range of
coordinates that are in view. Coordinates in the range −*scale* to *scale*
should be visible. If axes are drawn, they extend from −*scale* to scale along
each coordinate axis. The y-axis (green) points upward, the z-axis (blue) points out of the screen,
and the x-axis (red) points to the right.