Elements of descriptive geometry, with applications to isometric projection and othe forms of one-plane projection; a text-book for colleges and ingineering schools by O. E. Randall.

20

DESCRIPTIVE GEOMETRY

Fig. 27 represents a plane in the third quadrant, perpendicular
to V but oblique to H. Under these conditions the horizontal trace
must be perpendicular to G-L and the vertical trace must make
the same angle with G-L that the plane makes with H.
Fig. 28 shows how the traces of the plane in Fig. 27 will appear
after H and V take their position of coincidence.

FIG. 27

FIG. 28

8 -

8'

FIG. 29

FIG. 30

Fig. 29 represents a plane in the third quadrant and parallel to
G-L. Its traces then must both be parallel to G-L.
Fig. 30 shows how the traces of the plane in Fig. 29 will appear
after H and V take their position of coincidence.
In all the foregoing cases, in order that the diagrams may be
more easily understood, only limited portions of the planes have
been taken into consideration; but planes must be regarded as