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Class 12 Vector Algebra · Long Answer3 Marksorthogonality

Class 12 Maths · Vector Algebra · Long Answer #112

Find a unit vector perpendicular to a+b and a−b, where a=(1,1,1), b=(1,2,3).

✅ Step-by-Step Solution

Final Answer: ±(−1,2,−1)/√6
  1. Compute a+b=(2,3,4), a−b=(0,−1,−2).
  2. Their cross product is (−2,4,−2)=2(−1,2,−1).
  3. Its norm is 2√6.
  4. The unit normals are ±(−1,2,−1)/√6.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] Compute a+b=(2,3,4), a−b=(0,−1,−2).
  • [1 mark] Their cross product is (−2,4,−2)=2(−1,2,−1).
  • [1 mark] Its norm is 2√6.
  • [0.5 marks] The unit normals are ±(−1,2,−1)/√6.

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