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JEE Advanced 2021Paper 2
Exam
JEE Advanced
Year
2021
Paper
Paper 2
Subject
Mathematics
Chapter
Parabola

JEE Advanced 2021 · Paper 2 · Mathematics · Parabola

Let E denote the parabola y ^ 2 = 8x . Let P = (- 2, 4) , and let Q...

Let EE denote the parabola y2=8x.{y}^{2} = 8x . Let P=(−2,4)P = \left(- 2, 4\right), and let QQ and Q′{Q}^{'} be two distinct points on EE such that the lines PQPQ and PQ′P{Q}^{'} are tangents to EE. Let FF be the focus of EE. Then which of the following statements is (are) TRUE?Let E denote the parabola y ^ 2 = 8x . Let P = (- 2, 4) , and let Q and Q ^ ' be two distinct points on E such that the

Options

  1. AThe triangle PFQPFQ is a right-angled triangle
  2. BThe triangle QPQ′QP{Q}^{'} is a right-angled triangle
  3. CThe distance between PP and FF is 525\sqrt{2}
  4. DFF lies on the line joining QQ and Q′{Q}^{'}

Correct answer

A. The triangle PFQPFQ is a right-angled triangle

Step-by-step solution

Let E denote the parabola y ^ 2 = 8x . Let P = (- 2, 4) , and let Q and Q ^ ' be two distinct points on E such that the

y2=8x{y}^{2} = 8x

⇒a=2,⇒ a = 2, Focus F(2,0),F\left(2, 0\right), and Directrix x=−2x = - 2

∵P(−2,4)∵ P\left(- 2, 4\right) lies on directrix

⇒QQ′⇒ Q{Q}^{'} will be a focal chord and tangents are mutually perpendicular.

⇒\DeltaQPQ′⇒ \DeltaQP{Q}^{'} is right angled.

Also the portion between point of contact and directrix of parabola subtends right angle at the focus.

So, △PFQ△ PFQ is a right- angled triangle.

PF=(−2−2)2+(4−0)2=42PF = \sqrt{{\left(- 2 - 2\right)}^{2} + {\left(4 - 0\right)}^{2}} = 4\sqrt{2}

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