Legendre, A. M. (Adrien Marie), 1752-1833, Brewster, David, Sir, 1781-1868, Davies, Charles, 1798-1876 · New York, Wiley & Long · leaf 139
BOOK VI. 130 mains AD<AC. The two sides AS, SD, are equal lo thetwo AS, SC ; the third side AD is less than the third side AC ;Ihereture the an;rle ASD<ASC (Book I. Prop. IX. Sch.).Adding BSl) = BSC, we shall have ASD + BSD or ASB<ASC + B«C. … PROPOSITION XX. THEOREM. • Tlie sum of the plane angles which form a solid angle is alwaysless than four right angles. Cut the solid angle S by any planeABCDE ; from O, a point in that plane,draw to the several angles the straightlines AG, OB, OC, 01), OE. The sum of the angles of the trianglesASB,…
Trigonometry · Geometry
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