Plane and solid analytic geometry; an elementary textbook (1904)
Ashton, Charles Hamilton, 1866-1936 · New York, C. Scribner's Sons · leaf 61
their positive directions. But when thelines are given by their equations and no convention is used to fix their posi-tive directions, it is con-venient to define the an-gle which one line makeswith another as the angleformed by going from thesecond line to the first inthe positive direction… … Ch. IV, §31] THE STRAIGHT LINK 45 find the angle which AB makes with MN. Let the equa-tions of AB and MN be given in the form y = hx + hv and y = l2x + b2. From the figure # = y{ — y2, and tan g = tan (7.-7.) = tan 7, - tan 7, , 1 + tan yx tan y2 Hence tan0 = ^f-^-. [11, a] If the equations are…
Geometry, Analytic
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