Godfrey, C. (Charles), 1873-1924, Siddons, A. W. (Arthur Warry) joint author · Cambridge, University Press · leaf 76
is harmonic. [Through C and C draw parallels to OD, and use Exs. 222, 223.] Definition. A system of lines through a point is called apencil. The point is called the vertex of the pencil. Definition. Any straight line drawn across a system of linesis called a transversal. HARMONIC SECTION 57 Theorem… … fig. 32. Let O be the vertex of the pencil. Let a straight line cut the rays of the pencil at A, C, B, D. Through C and C draw straight lines || to OD, cutting OAat P, P and OB at Q, Q. •/ PC is II to OD. .. As APC, AOD are similar. AC _ PC •• AD~OD also As BQC, BOD are similar. . CBQC t , 1 DB~OD*…
Geometry, Modern
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