Problem V.
To Draw a Horizontal Line, Given in Position and Magnitude, by Means of Its Sight-Magnitude and Dividing-Points
Let A B (Fig. 16.) be the given line.
Find the position of the point A in a.
Find the vanishing-point V, and most convenient dividing-point M, of the line A B.
Join a V.
Through a draw a horizontal line a b′ and make a b′ equal to the sight-magnitude of A B. Join b′ M, cutting a V in b.
Then a b is the line required.