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 42
ame point G and parallel to GB^which is impossible (a. 13): hence, EGB + GHB is equalto two right angles. In the same manner it may be provedthat HGA+GHC is equal to two right angles. Cor. 1. If HGB is a right angle, GHB will be a rightangle also: therefore, every straight line 2^^y^^dicular to… … 38 GEOMETKY The sum HGB + GHD isal to two right angles. Butthe sum HGB+HGA is also equal to two right angles. But / equal to two right angles (p. 1). Y Taking from each the angle HGB^ / and there remains AGH=GHD. C -g D In the same manner we may / prove that GHC=HGB. F Cor. 3. If a straight line…
Geometry · Trigonometry
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