Veblen, Oswald, 1880-1960, Young, John Wesley, 1879-1932 · Boston, New York [etc.] Ginn and Company · leaf 75
, CD). Two throws are said to be equal, provided they areprojective; in symbols, T (AB, CD) = T (AB, CD), provided we haveABCD ^ ABCD. The last theorem then states the equality of throws : T(AB, CD) = T(BA,DC) = T(CD, AB) = T(DC, BA). The results of the last two theorems may be stated in the… … §23] PROJECTIVITY 61 Theorem 2. If 1, 2, 3, 4 are anV four distinct elements of a one-dimensional primitive form, there exist projective transformationswhich will transform 1234 ^nt° anV one °f ^ie following permuta-tions of itself: 1234, 214$, S412, 4321. A projective transformation has been…
Geometry, Projective
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