设Q(x,y)ï¼ç´çº¿æ¹ç¨ä¸ºy=kx+m
代å
¥æ¤åæ¹ç¨x^2/a^2+y^2/b^2=1å¾
x^2/a^2+(kx+m)^2/b^2=1
æ´çå¾
(b^2+a^2k^2)x^2+2a^2kmx+a^2m^2-a^2b^2=0
注æç´çº¿æ¯å线ï¼å æ¤æ
â³=(2a^2km)^2-4(b^2+a^2k^2)(a^2m^2-a^2b^2)=0
a^2k^2m^2-(b^2+a^2k^2)(m^2-b^2)=0
a^2k^2m^2-b^2m^2-a^2m^2k^2+b^4+a^2b^2k^2=0
å æ¤æ
-b^2m^2+b^4+a^2b^2k^2=0
-m^2+b^2+a^2k^2=0
k^2=(b^2-m^2)/a^2
k=屉(b^2-m^2)/a (1)
注æå°â AQB=α
tanα=|k1-k2|/(1+k1k2)
=[2â(b^2-m^2)/a]/[1-(b^2-m^2)/a^2] (2)
ç±(1)(2)å¯å¾k,m
代å
¥å°±å¯å¾Qæ¹ç¨ï¼å¥½è±¡å¾éº»ç¦
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