JEE Main 2020 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 8 January 2020, Shift 1, Maths Q66

Question 66 of 75 in this shift, Maths question 16 of 25, Section A.

Let the volume of a parallelopiped whose coterminous edges are given by

\vec{u}=\hat{i}+\hat{j}+\lambda\hat{k}

\vec{v}=\hat{i}+\hat{j}+3\hat{k}

and

\vec{w}=2\hat{i}+\hat{j}+\hat{k}

be 1 cu. unit. If

\theta

be the angle between the edges

\vec{u}

and

\vec{w}

, then

\cos\theta

can be :

(1) $\frac{5}{7}$
(2) $\frac{7}{6\sqrt{6}}$
(3) $\frac{7}{6\sqrt{3}}$ Official answer
(4) $\frac{5}{3\sqrt{3}}$

Official answer

Option 3

NTA final key (Jan 2020).

Chapter: Vector Algebra
Topic: Triple Products
Idea tested: STP Geometric Interpretation

Same topic in other shifts

All Triple Products questions

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8 Apr 2023, Shift 2 · Q16Let the vectors $\vec{u}_1 = \hat{i} + \hat{j} + a\hat{k}$ , $\vec{u}_2 = \hat{i} + b\hat{j} + \hat{k}$ and…HardSingle correct
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16 Mar 2021, Shift 2 · Q84Let $\vec c$ be a vector perpendicular to the vectors $\vec a=\hat i+\hat j-\hat k$ and $\vec b=\hat i+2\hat j+\hat k$ . If…MediumNumerical value

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 42 of the 174 JEE Main shifts held from 2017 to 2026.