Newcomb, Simon, 1835-1909 · New York, H. Holt and company · leaf 58
t Lines. I. If, in the general equation of the straight line, Ax -\- By -^ C = 0, the coeflBcients A and B areof opposite signs, x must in-crease with y, the line makesan acute angle with the axis ofX, and its positive direction isQin the first or third quadrant.QR is such a line. II. If A and B… … THE STRAIGHT LINE. 43 III. If A vanishes, the equation may be reduced to y = 7> ~ ^ constant, while X may have any value whatever. The line is then parallel to the axis of X and at the dis-tance — -^ from it. IV. In the same way, the equation of a line parallel to the axis of Y is a; = a…
Geometry, Analytic
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