Veblen, Oswald, 1880-1960, Young, John Wesley, 1879-1932 · Boston, New York [etc.] Ginn and Company · leaf 247
nned is obviouslyprojective with the scale on a line, it is not necessary to derive againthe fundamental properties of addition and subtraction, multiplicationand division. It is clear from this consideration that the points of aconic form a field with reference to the operations just defined.… … Pig. 95 preceding discussion that if a number x satisfies the equation x2= a,the tangent to the conic at the point x must pass through the inter-section of the lines Ooo and 1 a (fig. 95). A member a will thereforehave a square root in the field if and only if a tangent can be drawn to §81] SCALE…
Geometry, Projective
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