JEE Main Maths · Vector Algebra

Lagrange's Identity

Lagrange's Identity (Vector Algebra) was asked 3 times in 3 JEE Main shifts, 2023–2024, out of the 42 shifts Lumi analysed. 1 of the 3 had a numerical answer.

Times asked: 3; in 3 shifts
Years: 2023–2024
Usual format: Single correct; Multi-step
Pattern: Occasional; repeats across shifts

How it is asked

Vector magnitudes from dot product and angle
Angle between vector and cross-product combination

Difficulty

Easy 0Medium 3Hard 0

Where it sits

Chapter: Vector Algebra. Topic: Cross Product, 32 questions over 11 ideas.

All 3 questions

Newest first, each with its options and official answer.

30 Jan 2024, Shift 2 · Q19Let $\vec{a} = \hat{i} + \alpha\hat{j} + \beta\hat{k}$ , $\alpha, \beta \in \mathbb{R}$ . Let a vector $\vec{b}$ be such that the angle…MediumSingle correct
31 Jan 2024, Shift 1 · Q30Let $\vec{a}$ and $\vec{b}$ be two vectors such that $|\vec{a}|=1,\ |\vec{b}|=4$ , and $\vec{a}\cdot\vec{b}=2$ . If…MediumNumerical value
6 Apr 2023, Shift 1 · Q16Let $\vec a=2\hat i+3\hat j+4\hat k$ , $\vec b=\hat i-2\hat j-2\hat k$ and $\vec c=-\hat i+4\hat j+3\hat k$ . If $\vec d$ is a vector…MediumSingle correct