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The Shadow of an Inclined Plane
The two portions of this inclined plane which cast the shadow are first the side fbd, and second the farther end abcd. The points we have to find are the shadows of a and b. From luminary L draw La, Lb, and from F, the foot, draw Fc, Fd. The intersection of these lines will be at a·b·. If we join fb· and db· we have the shadow of the side fbd, and if we join ca· and a·b· we have the shadow of abcd, which together form that of the figure.
Fig. 279.