Osgood, William F. (William Fogg), 1864-1943, Graustein, William C. (William Caspar), 1888-1941, joint author · New York : The Macmillan Company · leaf 319
YTIC GEOMETRY be (iCi, 2/1). The slope of D is then A = yi/x^. From (2), § 2,the slope A of the conjugate diameter D is Consequently, the equation of D can be written in the form(2) ( ay, hx It follows that D is parallel to the tangent to the ellipse at (xi, yi). In other words, the tan-gents at… … Fig. 9 _ayj hxA «2/i hx^a We summarize the foregoing results in a theorem. Theorem 7. If {x^, ?/i) is one extremity of a diameter D ofthe ellipse (1), then (2) is the equation of the conjugate diameterD, and one extremity (cc/, yi) of D is (3) 3. / _ «2/i 2/1 , _hxi a Suppose, now, that we denote…
