An Eccentricity from a 120° Angle

★ 7/10Reflectionconic sectionsSymmetry

Problem

The hyperbola C:x2a2−y2b2=1C:\dfrac{x^2}{a^2}-\dfrac{y^2}{b^2}=1 (a>0a>0, b>0b>0) has right focus FF. Let AA be a point on the right branch of CC, and let DD, EE be the reflections of AA across the origin and across the xx-axis respectively. Given EF∥ADEF\parallel AD and ∠AFE=120∘\angle AFE=120^\circ, find the eccentricity of CC.

Answer

Solution

Difficulty7/10
TopicsReflection, conic sections, Symmetry

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