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A> B> 0,点P(3,4)X ^ 2 / ^ 2 + Y ^ 2 / B ^ 2 = 1
9 / ^ 2 +16 / B ^ 2 = 1. . (1)
两个焦点F1,F2,如果PF1,
F1,⊥PF2(-C,0),F2(C,0)
K( PF1)= 4 /(1 + C),K(F2)= 4 /(3-C)
K(F1)* K(F2)= -1
[4 /(1 + C )] * [4 /(3-C)] = -1
C ^ 2 = 25
^ 2-B ^ 2 = 25 . (2)
B ^ 2 = 20 ^ 2 = 45
椭圆型?方程:
X ^ 2/45 + Y ^ 2/20 = 1
1年前
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