FIGURE 13.

PLANE PROJECTION PROBLEM

SOLUTION.

The lines drawn in step 3 define the right side view of plane 1-2-3-4.

In line theory we found that the end view of a line was a double-point. A similar

situation appears in the plane theory, which is explained by the following axiom:

This may be verified by holding a sheet of paper horizontal to the ground and

rotating it until you are looking directly at one edge. Although it is a plane,

the sheet appears as a line.

h. * Curves*.

So far, we have considered only straight lines.

Point, line, and

plane projection theory may be extended to include curved lines if we consider the

following axioms: