The second step in constructing the solid formed with square cross sections is to construct the two top edges. The two bottom edges lie in the xy-plane: the segment from (1,0,0 to (5,0,0) and the part of the parabola between x=1 to x=5.
These edges use the CURVE[ ] command. The near edge is CURVE[ t , 0 , f(t) , t , 1 , 5 ]. The back edge is CURVE[ t , f(t) , f(t) , t , 1 , 5 ].
