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Vector Algebra

Mathematics

Useful for: UPSC NDA/NA

Overview

Vectors have magnitude and direction; dot and cross products measure angles, projections, areas and perpendicularity.

Key points

  • Magnitude of (a, b, c) = √(a² + b² + c²).
  • Dot product a · b = |a||b| cos θ; perpendicular vectors have dot product zero.
  • Cross product magnitude |a × b| = |a||b| sin θ; it is perpendicular to both vectors.
  • i · j = 0 and i × j = k.
  • Unit vector = vector ÷ its magnitude.
  • Area of a parallelogram = |a × b|.

Practice MCQs

  1. From the perspective of definition and scope, which one of the following statements about Vector Algebra is correct?

    1. Vector Algebra is unrelated to institutions, processes or real-world applications.
    2. Vector Algebra has no exceptions or limitations in exam analysis.
    3. Vector Algebra questions reward a formula-first approach and accurate algebraic manipulation.
    4. Do not apply a memorized Vector Algebra formula without checking its conditions.

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    Answer: (c) Vector Algebra questions reward a formula-first approach and accurate algebraic manipulation.. Vector Algebra questions reward a formula-first approach and accurate algebraic manipulation.

  2. Consider the following statements on Vector Algebra and Probability, focusing on definition and scope: 1. Do not apply a memorized Vector Algebra formula without checking its conditions. 2. Do not apply a memorized Probability formula without checking its conditions. Which of the statements given above is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2

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    Answer: (d) Neither 1 nor 2. Neither statement is correct; both are common misconceptions.

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