Modern geometry . be two eqtdcross pencils, and ifX, Y, z be coUinear, then w is on the line fig. 78. If W does not lie on XYZ, let PW, QW cut XYZ in A, B respectively. Then {XY, ZA} = P {XY, ZW} = Q {XY, ZW} = {XY, ZB}. XZ . AY _ XZ ? BY ~ , AY BY•• XA~XB .. A and B coincide, .•. W lies on XYZ. CROSS-RATIO 133 Theorem 56. If two equicross pencils p {abcd}, q {abcd} have a rayPQA in common, then BCD are coUinear.

---

Size: 1704px × 1467px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: ., bookauth, bookcentury1900, bookdecade1900, bookidcu31924001083090