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a 7 MI JD 
A) T Xu 7 722 
Ayo "3291 P2 
Aj ® Tus TR 
and A7 x12 ^ a "2. 
Segmented Line - Figure 4 shows a segmented line, ABCD, imaged in a photograph 
as the line abcd. The anharmonic ratio of ABCD is given by: 
; - BD fuc (15) 
AD AC 
The image line, abcd, must necessarily have the same anharmonic ratio, 2, since a projective 
relationship exists between the line in object space and its image. Hence, 
. bi / be 
T ad / ac (16) 
Ray 
-~ Dofn : 
   
     
Photograph 
Figure 4