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Saturday, 31 October

JEE Main 2021 · MathsMultiple choiceSingle correctHardMulti-step

JEE Main 26 August 2021, Shift 1, Maths Q71

Question 71 of 90 in this shift, Maths question 11 of 30, Section A.

The sum of solutions of the equation cos⁡x1+sin⁡x=∣tan⁡2x∣\frac{\cos x}{1+\sin x} = |\tan 2x|, x∈(−π2,π2)−{π4,−π4}x \in \left(-\frac{\pi}{2}, \frac{\pi}{2}\right) - \left\{\frac{\pi}{4}, -\frac{\pi}{4}\right\} is :
  1. (1)π10\frac{\pi}{10}
  2. (2)−11π30-\frac{11\pi}{30}Official answer
  3. (3)−7π30-\frac{7\pi}{30}
  4. (4)−π15-\frac{\pi}{15}

Official answer

Option 2

NTA final key.

Chapter
Trigonometric Functions
Topic
General Solutions
Idea tested
Modulus Trigonometric Equations

Same idea in other shifts

Asked 3× in all
  1. 25 Jul 2022, Shift 1 · Q18The number of solutions of ∣cos⁡x∣=sin⁡x|\cos x|=\sin x, such that −4π≤x≤4π-4\pi\le x\le4\pi is :EasySingle correct
  2. 4 Aug 2021, Shift 2 · Q79The number of solutions of the equation ∣cos⁡x∣=cos⁡x−2sin⁡x, −2π≤x≤2π|\cos x|=\cos x-2\sin x,\,-2\pi\le x\le2\pi, isMediumSingle 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.