JEE Main 2021 · MathsMultiple choiceSingle correctMediumCalculation

JEE Main 25 February 2021, Shift 2, Maths Q79

Question 79 of 90 in this shift, Maths question 19 of 30, Section A.

\mathrm{cosec}\left[2\cot^{-1}(5) + \cos^{-1}\left(\frac{4}{5}\right)\right]

is equal to :

(1) $\frac{56}{33}$
(2) $\frac{65}{33}$
(3) $\frac{65}{56}$ Official answer
(4) $\frac{75}{56}$

Official answer

Option 3

NTA final key.

Chapter: Inverse Trigonometric Functions
Topic: Inverse Trig Identities
Idea tested: Trig of Sum of Inverse Trig Functions

Same idea in other shifts

Asked 4× in all

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29 Jun 2022, Shift 1 · Q26…MediumNumerical value
30 Jun 2022, Shift 1 · Q19Let $\alpha = \tan\left(\frac{5\pi}{16}\sin\left(2\cos^{-1}\left(\frac{1}{\sqrt{5}}\right)\right)\right)$ and…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.