Question

Which condition defines an identity matrix?

Options

• \[a_{ij}=1\] if \[i=j\] and \[a_{ij}=0\] if \[i\ne j\]

• \[a_{ij}=0\] if \[i=j\] and \[a_{ij}=1\] if \[i\ne j\]

• \[b_{ij}=k\] if \[i\ne j\]

• \[a_{ij}=0\] for all \[i\] and \[j\]

Answer 1

Entries on the diagonal have \[i=j\], and each such entry is \[1\]. For \[i\ne j\], the entries are outside the diagonal and equal \[0\].