A Min Focal Sum on a Chord

8/10Pole and PolarExtremaconic sections

Problem

The ellipse C:x2a2+y2b2=1C:\dfrac{x^2}{a^2}+\dfrac{y^2}{b^2}=1 (a>b>0a>b>0) has left and right foci F1F_1, F2F_2; the point M(1,32)M\left(1,\dfrac 32\right) lies on CC, and in F1MF2\triangle F_1MF_2, tanMF1F2=34\tan\angle MF_1F_2=\dfrac 34.

1. Find the equation of the ellipse CC. 2. A line ll through P(1,3)P(1,3) meets CC at two points AA and BB (with AA above BB). A point QQ on the segment ABAB satisfies PAPB=QAQB\dfrac{|PA|}{|PB|}=\dfrac{|QA|}{|QB|}. Find the minimum value of QF1+QF2|QF_1|+|QF_2|.

Answer

Solution

Difficulty8/10
TopicsPole and Polar, Extrema, conic sections

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