[Footnote 9: ] The sentence within brackets will not be repeated in succeeding statements of problems. It is always to be understood.] [Return to text]
[Footnote 10: ] In order to be able to do this, you must assume the distances to be small; as in the case of some object on the table: how large distances are to be treated you will see presently; the mathematical principle, being the same for all, is best illustrated first on a small scale. Suppose, for instance, P to be the corner of a book on the table, seven inches below the eye, five inches to the left of it, and a foot and a half in advance of it, and that you mean to hold your finished drawing at six inches from the eye; then T S will be six inches, T D a foot and a half, D C five inches, and C P seven.] [Return to text]
[p13]
][PROBLEM II.]
TO DRAW A RIGHT LINE BETWEEN TWO GIVEN POINTS.
Fig. 6.
Let A B, [Fig. 6.], be the given right line, joining the given points A and B.
Let the direct, lateral, and vertical distances of the point A be T D, D C, and C A.
Let the direct, lateral, and vertical distances of the point B be T D′, D C′, and C′ B.
Then, by [Problem I.], the position of the point A on the plane of the picture is