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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