An introduction to projective geometry and its applications; an analytic and synthetic treatment (1905)
Emch, Arnold, b. 1871 · New York, J. Wiley & sons; London, Chapman & Hall, limited · leaf 26
ation are indeed identical with the pre- B a2vious values of a and b. If - >—, a and b are conjugate complex numbers, i.e., the double-points of the involution are imaginary.In this case the middle point M of the involution is still real, a+b a since = - , and 2 r> MX-MY = (a-b) a2 B —… … Fig. 4. bolic in case of real double-points, elliptic in case of imaginarydouble-points, parabolic in case of coinciding double-points.
Geometry, Projective · Geometry, Analytic
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