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📐 Mathematics  ·  Vector Algebra  ·  JEE

If theta = 90 degrees and |a| = 3, |b| = 4, then |a x b| =

Answer: 12.

  • A 0
  • B 7
  • C 12
  • D 24

Correct answer: C. 12

Explanation: |a x b| = |a||b|sin(90) = 3 x 4 x 1 = 12. Cross product is maximum when vectors are perpendicular.

xya (4,1)b (2,3)a + b (6,4)

Triangle law of vector addition: placing vector b at the head of vector a, the diagonal from the start to the final head gives the resultant a + b.

Concept context

Vectors, dot product, cross product, and geometric applications

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