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Let A=[02yzxy−zx−yz]A = \begin{bmatrix} 0 & 2y & z \\ x & y & -z \\ x & -y & z \end{bmatrix} and II be an identity matrix of order 3. If ATA=IA^TA=I, then x2+y2+z2x^2+y^2+z^2 is equal to:

Solution

✅ Correct Option: 1

ATA=IA^TA = I means the columns of AA are mutually orthogonal unit vectors.

Column norms give 0+x2+x2=10+x^2+x^2 = 1, 4y2+y2+y2=14y^2+y^2+y^2 = 1, z2+z2+z2=1z^2+z^2+z^2 = 1.

So x2=12x^2 = \dfrac{1}{2}, y2=16y^2 = \dfrac{1}{6}, z2=13z^2 = \dfrac{1}{3}, and their sum is 11.

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