Elements of geometry and trigonometry. Revised and adapted to the course of mathematical instruction in the United States (1856)
Legendre, A. M. (Adrien Marie), 1752-1833, Davies, Charles, 1798-1876 · New York : A.S. Barnes · leaf 164
oints common to both planes, and consequently, istheir common intersection. rKOPOSITIOX IV. THEOREM. Lf a straiglit line he ijerpendicular to two straight lines at ihcirpoint of intersection^ it will he j^^^J^^ndicular to the planeof those lines. Let J/iV be the plane of the two lines BL\ CC, and… … For, throiigli P draw in theplane il//V, any straight line as PQ.Through any point of this line, asQ, draw BQO, so that BQ shallbe equal to QC (b. IV., prob. 5);draw AB, AQ, AC. The base BC being divided intotwo equal parts at the point ft thetriangle BPC gives (B. iv., P. 14:).…
Geometry · Trigonometry
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