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CBSE Class 12 Mathematics 2026 Main Paper 65/2/2 · Q222 Marksvector_median

CBSE Class 12 Mathematics 2026 Main Paper 65/2/2 · Question 22 (Vector Algebra)

For AB=(0,1,1) and AC=(3,−1,4), prove AD=(AB+AC)/2 where D is the midpoint of BC, then find |AD|.
Triangle ABC drawn to scale in its plane. D is halfway along BC and AD is the median.
Triangle ABC drawn to scale in its plane. D is halfway along BC and AD is the median.

✅ Step-by-Step Solution

Final Answer: AD=(3/2,0,5/2), length √34/2.
  1. Use AD=AB+BD and BD=BC/2.
  2. As BC=AC−AB, this gives AD=(AB+AC)/2=(3,0,5)/2.
  3. The length is √34/2.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] Use AD=AB+BD and BD=BC/2.
  • [1 mark] As BC=AC−AB, this gives AD=(AB+AC)/2=(3,0,5)/2.
  • [0.5 marks] The length is √34/2.

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