Q24 / 53 · NTA Abhyas (JEE Main) 2020 · Mathematics · Ellipse

If a number of ellipses whose major axis is x-axis and the minor axis is y-axis be described having the same length of the major axis as 2 but a variable minor axis, then the tangents at the ends of their latus rectum pass through fixed points whose distance from the centre is equal to 

  • A
    12 units
  • Correct answer
    B
    1 unit
  • C
    32 units
  • D
    2 units

Solution

Since the minor axis is variable, hence e is a variable quantity

Therefore the equation of the tangent to the ellipse can be written as xaea2+yb2ab2=1
⇒ex+y=a⇒y-a+ex=0
This line passes through the fixed point 0,a (where a=1)

Hence, distance fro the centre of the ellipse =1

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

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