Q18 / 40 · NTA Abhyas (JEE Main) 2020 · Mathematics · Hyperbola

From a point P, two tangents PA and PB are drawn to the hyperbola x2a2-y2b2=1. If the product of the slopes of these tangents is 1, then the locus of P is a conic whose eccentricity is equal to

  • A
    1
  • B
    2
  • Correct answer
    C
    2
  • D
    12

Solution

Let, P be h,k and the equation of tangent through P on the hyperbola is
y=mx±a2m2-b2
⇒k2-mh2=a2m2-b2
⇒h2-a2m2-2khm+k2+b2=0 where roots are m1 and m2

⇒k2+b2h2-a2=1=m1m2
⇒ locus is x2-y2=a2+b2
⇒ eccentricity =1+1=2

Hence, the correct answer is option: 'C'.

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