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Saturday, 31 October

JEE Main 2021 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 31 August 2021, Shift 1, Maths Q73

Question 73 of 90 in this shift, Maths question 13 of 30, Section A.

If p and q are the lengths of the perpendiculars from the origin on the lines, x cosec α−ysec⁡α=kcot⁡2αx\,\mathrm{cosec}\,\alpha-y\sec\alpha=\mathrm{k}\cot2\alpha and xsin⁡α+ycos⁡α=ksin⁡2αx\sin\alpha+y\cos\alpha=\mathrm{k}\sin2\alpha respectively, then k2\mathrm{k}^2 is equal to :
  1. (1)p2+2q2\mathrm{p}^2+2\mathrm{q}^2
  2. (2)p2+4q2\mathrm{p}^2+4\mathrm{q}^2
  3. (3)2p2+q22\mathrm{p}^2+\mathrm{q}^2
  4. (4)4p2+q24\mathrm{p}^2+\mathrm{q}^2Official answer

Official answer

Option 4

NTA final key.

Same idea in other shifts

Asked 2× in all
  1. 18 Mar 2021, Shift 2 · Q67Let the centroid of an equilateral triangle ABC be at the origin. Let one of the sides of the equilateral triangle be along the straight…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.