Legendre, A. M. (Adrien Marie), 1752-1833, Brewster, David, Sir, 1781-1868, Davies, Charles, 1798-1876 · New York, Wiley & Long · leaf 80
^AC^B0^—260 x CD. There are two cases. First. When the perpendicular falls withinthe triangle ABC, we have BDrrBC—CD,and consequently BD^-BCHCD^—2BCxCD (Prop. IX.). Adding AD- to each,and observing that the right angled trian-gles ABD, ADC, give ADHBD^=AB^, andADHCD^n^AC^ we have AB2-BC^+AC2—2BC X… … PROPOSITION XIII. THEOREM. In every obtuse angled triangle, the square of the side opposite t?ieobtuse angle is greater than the sum of the squares of the othertwo sides by twice the rectangle contained by the base and thedistance from, the obtuse angle to the foot of the perpendicularIçt fall from…
Trigonometry · Geometry
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