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.

186

DESCRIPTIVE GEOMETRY

parallel to a,-b,. The points E, K, G, and L, projected at (e,, e'),
(k,, c'), (g,, g'), and (1,, 1'), are the four points of intersection.
The auxiliary plane T cuts the sphere in a small circle whose
center is /I and whose diameter is equal to n,-o,. The same plane

FIG. 162

T cuts the cylinder in two elements, P-Q and R-Z, which are
parallel to A-B.
By passing a sufficient number of auxiliary planes we may locate
enough points to determine the required curve of intersection.
Since the auxiliary planes U and W, which are drawn tangent
to the cylinder, both intersect the sphere, there are, according to
Section 408, two distinct curves of intersection, as may be seen
from the drawing.
The visible and invisible portions of the curves may be determined by methods previously explained.