MCQ
If $\displaystyle \text{a}_{\text{ij}}=0\left (\text{i}\neq \text{j} \right )$ and $\displaystyle \text{a}_{\text{ij}}=1\left (\text{i}= \text{j} \right )$ then the matrix $\text{A}=\displaystyle \left [\text{a}_{\text{ij}} \right ]_{\text{n}\times\text{n}}$ is a $ ....... $ matrix :
  • A
    Null
  • Identity
  • C
    Scalar
  • D
    Triangular

Answer

Correct option: B.
Identity
The elements $\text{a}_\text{ij}$ ​ of a matrix where $i = j$ lie along its diagonal and
the elements $\text{a}_\text{ij}$ of a matrix where $\text{i}\neq\text{j}$ are not along the diagonal.
As the diagonal elements are $11$ and the rest of the elements are $0,$ the matrix $A$ is an identity matrix.

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