A Maximal Inscribed Triangle

Problem

The ellipse E ⁣:x24+y2=1E \colon \dfrac{x^2}{4} + y^2 = 1 has left and right foci F1,F2F_1, F_2. A moving point PP on EE is such that lines PF1PF_1 and PF2PF_2 meet EE again at points QQ and RR respectively.

1. When PP is the top vertex of EE, find the area of triangle PQRPQR. 2. Prove that the area of triangle PQRPQR is maximized exactly when PP is the top or bottom vertex of EE.

Answer

Solution

Difficulty7/10
TopicsLaw of Sines, trigonometry, Extrema, Trigonometric Identities, conic sections, analytic geometry

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