Example · Undergraduate

Terms

TermThis exampleWhy
entrywise exponential \[\begin{bmatrix} 1 & 1 \\ 1 & 1 \end{bmatrix}\] The entrywise exponential of the $2 \times 2$ zero matrix is the matrix of ones, because $e^0 = 1$ for each entry.
matrix exponential \[e^{0} = \begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}\] The matrix exponential of the $2 \times 2$ zero matrix is the identity matrix, because every term of $I + 0 + 0^2 / 2! + \cdots$ after $I$ is zero.
matrix rank $\operatorname{rank} 0 = 0$ The $2 \times 2$ zero matrix has rank $0$, because its column space is $\setdef{0}$.
nullity $\operatorname{nullity} 0 = 2$ The $2 \times 2$ zero matrix has nullity $2$, because it sends every vector in $\reals^2$ to $0$.
singular matrix ✓ The $2 \times 2$ zero matrix is singular, because its determinant is $0$.
defective matrix ✗ The $2 \times 2$ zero matrix is not defective, because its eigenvalue $0$ has multiplicity $2$ and every nonzero vector is an eigenvector, so it has $2$ linearly independent eigenvectors.

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