Tangents from a Line

Problem

The hyperbola E ⁣:x2a2y2b2=1E \colon \dfrac{x^2}{a^2} - \dfrac{y^2}{b^2} = 1 (a>0a > 0, b>0b > 0) has a vertex on the line l ⁣:y=x+1l \colon y = x + 1 and eccentricity 5\sqrt{5}.

1. Find the standard equation of the hyperbola EE. 2. Call a line a tangent of EE if it meets EE in exactly one point and is not parallel to an asymptote; the common point is the point of tangency. Let TT be a point on ll from which exactly two tangents to EE can be drawn, touching EE at PP and MM respectively.

  1. If tt is the xx-coordinate of TT, find the range of possible values of tt.
  2. Let lines TPTP and TMTM meet the line x=1x = -1 at QQ and NN respectively. Prove that the intersection of lines PNPN and MQMQ lies on a fixed line.

Answer

Solution

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

Whiteboard

Your sketch is saved only in this browser. To share it, export your drawing as an image (whiteboard menu → Export as → PNG), then upload that image in the comments below.

Discussion

Ask questions, share alternate solutions, and use LaTeX freely.

0 comments
Log in to join the discussion.

No comments yet.