Q58 / 125 · BITSAT 2018 · Mathematics

A tangent drawn to hyperbola x2a2-y2b2=1 at Pπ6 forms a triangle of area 3a2 square units, with coordinate axes. If the eccentricity of hyperbola is e, then the value of e2-9 is

  • A
    9
  • B
    10
  • C
    11
  • Correct answer
    D
    8

Solution

The point Pπ6 is asecπ6,btanπ6 or P2a3,b3

∴ Equation of tangent at P is x3a2-y3b=11$

∴ Area of the triangle =12×3a2×3b=3a2

∴ ba=4

e2=1+b2a2=17

Now, e2-9=17-9=8

Hence, option (d) is correct.

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

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