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NCERT Class 12 · Ch 3 Miscellaneous Exercise · Q3

NCERT Class 12 Maths · Chapter 3 Matrices · Miscellaneous Exercise Question 3

Find all real x,y,z for A=\(\left[\begin{matrix}0 & 2 y & z\\x & y & - z\\x & - y & z\end{matrix}\right]\) to satisfy AᵀA=I.

💡 Concept Hints

  1. Check the matrix orders and the meaning of the requested operation before calculating.
  2. Keep row and column indices in order. Compare corresponding entries only after the matrix expressions have compatible dimensions.

✅ Step-by-Step Solution

Final Answer: x=±1/√2, y=±1/√6, z=±1/√3, with signs independent.
  1. The three columns are pairwise orthogonal: each cross dot product cancels to zero.
  2. Their squared norms are 2x²,6y²,3z², so AᵀA=\(\left[\begin{matrix}2 x^{2} & 0 & 0\\0 & 6 y^{2} & 0\\0 & 0 & 3 z^{2}\end{matrix}\right]\).
  3. Equating to I gives x²=1/2,y²=1/6,z²=1/3. Either sign is allowed independently, yielding eight triples.

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