Legendre, A. M. (Adrien Marie), 1752-1833, Brewster, David, Sir, 1781-1868, Davies, Charles, 1798-1876 · New York, Wiley & Long · leaf 137
PDperfxîndicular to PB ; then, be-cause the jilanes are perpendicu-lar, the angle APD is a right an-glf; ; therefore, the line AP isperp(Tidi(:ular to th(î two straightIJiM.s PB, PD ; therefore it is perpendicular to their plane MN(Prop. IV.). Cor. If the plane; AlJis perpendicular to the plane… … ns GEOMETRY. pendicular lo PB the common intersection, and this AP, at thesame time, would he perpendicular to the plane MN; thereforeat the same point P there would be two perpendiculars to theplane MN, wiiicii is impossible (Prop. IV» Cor. 2.). PEOPOSÏTION XVni. THEOREM. Iftwoplawes are…
Trigonometry · Geometry
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