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JEE Main 202227 JulyEvening Shift
Exam
JEE Main
Year
2022
Date
27 July
Shift
Evening Shift
Subject
Mathematics
Chapter
Parabola

JEE Main 2022 · 27 July · Evening Shift · Mathematics · Parabola

If the length of the latus rectum of a parabola, whose focus is (a,...

If the length of the latus rectum of a parabola, whose focus is (a,a)andthetangentatitsvertexis\left(a, a\right) and the tangent at its vertex isx + y = a,is, is16,then∣a∣, then \left|a\right| is equal toIf the length of the latus rectum of a parabola, whose focus is (a, a) and the tangent at its vertex is x + y = a , is

Options

  1. A222\sqrt{2}
  2. B232\sqrt{3}
  3. C424\sqrt{2}
  4. D44

Correct answer

C. 424\sqrt{2}

Step-by-step solution

Given the equation of tangent at vertex is x+y=ax + y = a

and the focus is \left(a, a\right)</p><p><imgsrc="https://cdn−question−pool.getmarks.app/pyq/jeemain/957085c2−8e98−4eb5−80fc−448d1775f7a2−image.png"style="width:199px;height:200px;"/></p><p>Nowtheperpendiculardistancefromfocustotangentis</p><p></p><p><img src="https://cdn-question-pool.Quantrex.app/pyq/jee_main/957085c2-8e98-4eb5-80fc-448d1775f7a2-image.png" style="width: 199px; height: 200px;" /></p><p>Now the perpendicular distance from focus to tangent is </p><p>\dfrac{\left|a + a - a\right|}{\sqrt{2}} = \dfrac{\left|a\right|}{\sqrt{2}}</p><p>Alsogivenlengthoflatusrectum</p><p>Also given length of latus rectum= 16</p><p>i.e.∣a2∣=164=4</p><p>i.e. \left|\dfrac{a}{\sqrt{2}}\right| = \dfrac{16}{4} = 4

⇒∣a∣=42⇒ \left|a\right| = 4\sqrt{2}

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