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JEE Main 2020 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 9 January 2020, Shift 1, Maths Q69

Question 69 of 75 in this shift, Maths question 19 of 25, Section A.

The value of

\cos^3\left(\frac{\pi}{8}\right)\cdot\cos\left(\frac{3\pi}{8}\right)+\sin^3\left(\frac{\pi}{8}\right)\cdot\sin\left(\frac{3\pi}{8}\right)

is :

(1) $\frac{1}{\sqrt{2}}$
(2) $\frac{1}{2}$
(3) $\frac{1}{2\sqrt{2}}$ Official answer
(4) $\frac{1}{4}$

Official answer

Option 3

NTA final key (Jan 2020).

Chapter: Trigonometric Functions
Topic: Trigonometric Identities
Idea tested: Product to Sum Formulas

Same idea in other shifts

Asked 2× in all

26 Aug 2021, Shift 2 · Q80The value of…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.