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Conic Triangle (Posted on 2014-10-17) Difficulty: 3 of 5

  
A line tangent to a hyperbola intersects its asymptotes at points L and N.
Let M be the intersection of the asymptotes.

Prove that the area of ΔLMN is a constant.
  

See The Solution Submitted by Bractals    
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Solution SOLUTION | Comment 1 of 3

Let the hyperbole equation be:
x*y=C
Let's C=1 to simplify  the proof.


The tangent to the curve in point P(x1,y1)  will be:

y-y1=-(1/x1^2)*(x-x1)

Getting OM  & ON  is obtained by  inserting Y=0 and X=0 respectively.

We get OM=2*x1
and ON=2*y1

So the area  will be
S= .5*OM*ON=.5*4*X1*Y1=2*X1*Y1=2

So
 S=2   - not related to coordinates of the point P.


Edited on October 18, 2014, 4:26 am
  Posted by Ady TZIDON on 2014-10-18 04:16:30

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