alleryThe identity matrix $I_n$ of order $n$ is:
AA diagonal matrix with all diagonal elements equal to 1 and others 0
BA matrix where rows equal columns
CA matrix with all elements equal to 1
DA matrix with all elements 0
Answer & Solution
Correct answer: A. A diagonal matrix with all diagonal elements equal to 1 and others 0
The $n \times n$ identity $I_n$ has $1$s on the main diagonal and $0$s everywhere else. It plays the role of the multiplicative identity: for any compatible $A$, $A \cdot I = I \cdot A = A$.
Option A (all 1s) is the $J$ matrix, sometimes called the all-ones matrix. Option C (all zeros) is the zero matrix, the additive identity.
Keep practising Matrices
Browse all Matrices questions for AP Intermediate 2nd Year, or explore more Mathematics topics.
Related questions
The inverse of a 2x2 matrix [[a,b],[c,d]] is (when det ≠ 0):If A is a 3×3 matrix with det(A) = 2, then det(2A):For A = [[2,0],[0,3]] (diagonal matrix), A² equals:If A = [[1,2],[3,4]], find det(A):The element a_23 of a matrix is located at:A square matrix A is symmetric if:The transpose of a 2x3 matrix is a:For a 3x3 identity matrix I, det(I) equals: