Conjugate Point Pairs

Problem

An ellipse EE centered at the origin OO with foci on the xx-axis passes through A(2,22)A\left(\sqrt{2}, -\dfrac{\sqrt{2}}{2}\right) and B(0,1)B(0, 1).

1. Find the standard equation of EE. 2. For an ellipse x2a2+y2b2=1\dfrac{x^2}{a^2} + \dfrac{y^2}{b^2} = 1 (with a>b>0a > b > 0), call points M(x1,y1)M(x_1, y_1) and N(x2,y2)N(x_2, y_2) on it a conjugate pair [M,N][M, N] if

x1x2a2+y1y2b2=0.\frac{x_1 x_2}{a^2} + \frac{y_1 y_2}{b^2} = 0.
  1. Prove there are exactly two points GG such that [A,G][A, G] is a conjugate pair of EE, and find their coordinates.
  2. Call these two points G1,G2G_1, G_2. A line ll through P(2,1)P(2, 1) meets EE at points CC and DD. Is there a fixed point QQ on the line G1G2G_1G_2 such that the product of the slopes of QCQC and QDQD is constant? If so, find QQ; if not, explain why.

Answer

Solution

Difficulty8/10
TopicsPole and Polar, conic sections, analytic geometry, Symmetry

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