A Constant Product of Slopes?

Problem

The ellipse C ⁣:x2a2+y2b2=1C \colon \dfrac{x^2}{a^2} + \dfrac{y^2}{b^2} = 1 (with a>b>0a > b > 0) has eccentricity 22\dfrac{\sqrt{2}}{2}, and the circle whose diameter is the minor axis of CC is tangent to the line y=ax+6y = ax + 6.

1. Find the standard equation of the ellipse CC. 2. The line l ⁣:y=k(x1)l \colon y = k(x-1) (with k0k \neq 0) meets CC at two points AA and BB. Through a point PP on CC, a line parallel to the xx-axis meets segment ABAB at a point QQ. Let kk' be the slope of line OPOP (where OO is the origin), and let S1,S2S_1, S_2 be the areas of triangles APQAPQ and BPQBPQ. If

APS2=BPS1,|AP| \cdot S_2 = |BP| \cdot S_1,

determine whether kkk \cdot k' is a constant, and justify your answer.

Answer

Solution

Difficulty7/10
TopicsAffine Transformation, conic sections, analytic geometry, Symmetry

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