Maths · Class 12 · Vector Algebra

Vector Algebra for JEE

Everything you need for this topic on one page: the ideas, the formulas, the traps, and free lectures that explain it well.

Last updated: 26 October 2026

Direct answer

Vectors and scalars, addition, components, dot and cross products, scalar and vector triple products.

Vectors and scalars, addition, components, dot and cross products, scalar and vector triple products.

Key ideas

Vector Algebra: what you must understand

  • Dot product measures projection; zero for perpendicular vectors
  • Cross product is perpendicular to both; magnitude = area of parallelogram
  • Scalar triple product = volume of parallelepiped
  • Coplanar vectors: [a b c] = 0
Formula sheet

Must-know formulas for Vector Algebra

  • a·b = |a||b| cosθ
  • |a × b| = |a||b| sinθ
  • Projection of a on b = a·b/|b|
  • a × (b × c) = (a·c)b − (a·b)c
Print

One-page formula sheet

Printable Vector Algebra formula sheet: formulas, key ideas and traps on one page. Save it as a PDF for offline revision.

Avoid

Common mistakes students make

  • Cross product order (a × b = −b × a)
  • Using dot product for area
  • Wrong expansion of vector triple product
For the exam

How this topic is asked in JEE

Appears in almost every JEE Main shift. Quick, formula-driven questions. Combine with 3D geometry.

NCERT map

Where Vector Algebra is in NCERT

Chapter names follow the current rationalised NCERT textbooks. Read these sections before solving PYQs.

ClassBookChapterSections JEE asks from
Class 12Mathematics Part IIVector AlgebraTypes of Vectors; Addition of Vectors; Multiplication of a Vector by a Scalar; Product of Two Vectors; Scalar (or dot) product of two vectors; Vector (or cross) product of two vectors
JEE Advanced level

A JEE Advanced-level example on Vector Algebra

Question. Let a = 2i + j - k and b = i - 2j + 2k. If c is a vector such that a · c = |c|, |c - a| = 2√2, and the angle between (a × b) and c is 30°, find |c|.

Show solution
  1. Find |a|² = 4 + 1 + 1 = 6
  2. Use |c - a|² = 8, which expands to |c|² - 2(a · c) + |a|² = 8
  3. Substitute a · c = |c| to get |c|² - 2|c| + 6 = 8, so |c|² - 2|c| - 2 = 0
  4. Solve the quadratic: |c| = (2 ± √12)/2 = 1 ± √3
  5. Since magnitude must be positive, |c| = 1 + √3

Answer: |c| = 1 + √3

This example was solved twice independently and both solutions agree.

Free lectures

Best free lectures for Vector Algebra

Full-chapter free lectures picked from YouTube search results by views, from established JEE channels (mostly in Hinglish). Use the subtopic list to jump straight to the part you need (timestamps come from each video's own chapter list). Watch one, then solve PYQs the same day.

Practise

Where to practise for free

FAQs

Frequently asked questions

Is Vector Algebra important for JEE Main 2027?

Appears in almost every JEE Main shift. It is part of the official 'Vector Algebra' unit in the JEE Main 2027 syllabus.

What are the most important formulas in Vector Algebra?

a·b = |a||b| cosθ; |a × b| = |a||b| sinθ; Projection of a on b = a·b/|b|.

How should I study Vector Algebra for JEE?

Understand the key ideas from NCERT or one full lecture, learn the formula sheet, then solve 25–30 past JEE questions on the topic. Quick, formula-driven questions. Combine with 3D geometry.

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