JEE Main 2021 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 31 August 2021, Shift 1, Maths Q77

Question 77 of 90 in this shift, Maths question 17 of 30, Section A.

\mathrm{cosec}18^\circ

is a root of the equation :

(1) $x^2-2x-4=0$ Official answer
(2) $x^2-2x+4=0$
(3) $x^2+2x-4=0$
(4) $4x^2+2x-1=0$

Official answer

Option 1

NTA final key.

Chapter: Trigonometric Functions
Topic: Trigonometric Identities
Idea tested: Values of Non-Standard Specific Angles

Same idea in other shifts

Asked 6× in all

8 Apr 2024, Shift 2 · Q20If the value of $\frac{3\cos 36^\circ + 5\sin 18^\circ}{5\cos 36^\circ - 3\sin 18^\circ}$ is $\frac{a\sqrt{5} - b}{c}$ , where a, b, c are…MediumSingle correct
27 Jan 2024, Shift 1 · Q30Let the set of all $a\in\mathbf{R}$ such that the equation $\cos 2x+a\sin x=2a-7$ has a solution be $[p, q]$ and…HardNumerical value
25 Jun 2022, Shift 2 · Q15The value of $2\sin(12^\circ) - \sin(72^\circ)$ is :MediumSingle correct
27 Jun 2022, Shift 2 · Q19 $\alpha=\sin 36^\circ$ is a root of which of the following equation?HardSingle correct
25 Jul 2021, Shift 2 · Q73The value of $\cot\frac{\pi}{24}$ is :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.