Given that I3 is a unit matrix of order 3, find |I3|

Given that I₃ is a unit matrix of order 3, find |I₃|

Correct Answer: Option C

Explanation

Recall that a unit matrice is a diagonal matrix in which the elements in the leading diagonal is unity. Therefore,
I₃ = (begin{pmatrix} 1 & 0 & 0 \ 0 & 1 & 0 \ 0 & 0 & 1 end{pmatrix})
I₃ = (+1begin{vmatrix} 1 & 0 \ 0 & 1 end{vmatrix} – 0begin{vmatrix} 0 & 0 \ 0 & 1 end{vmatrix} + 0 begin{vmatrix} 0 & 1 \ 0 & 0 end{vmatrix} )
I₃ = +1(1 – 0) – 0(0 – 0) + 0(0 – 0)
= 1(1)
= 1

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