Example 1, 2×2 Determinant
det of [[4, 2], [3, 1]]
- 1
Apply formula
det = (4)(1) − (2)(3) - 2
Compute
= 4 − 6 - 3
Result
= −2
For 2×2: det = ad − bc.
Compute determinant, inverse, transpose, addition, and multiplication of 2×2 matrices, with step-by-step explanations of every operation.
Matrix A (2×2)
Result
-2
det = (4)(1) − (2)(3) = -2
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2×2 Inverse Formula
Swap the diagonal entries, negate the off-diagonals, divide by the determinant. Works only when det ≠ 0.
A matrix is a rectangular array of numbers. The 2×2 matrix is the simplest non-trivial case and the foundation for understanding higher dimensions. Common operations include addition (entry-wise), multiplication (row · column), the determinant (a scalar that tells you whether the matrix is invertible), the inverse (the matrix that undoes multiplication), and the transpose (rows ↔ columns).
The most subtle is multiplication: it's NOT entry-wise. To get entry (i, j) of the product, take the dot product of row i of the first matrix with column j of the second. Order matters: AB ≠ BA in general.
Worked Examples
One example per supported operation, plus a singular-matrix case.
Example 1, 2×2 Determinant
det of [[4, 2], [3, 1]]
Apply formula
det = (4)(1) − (2)(3)Compute
= 4 − 6Result
= −2For 2×2: det = ad − bc.
Example 2, 2×2 Inverse
Inverse of [[4, 2], [3, 1]]
Determinant
det = (4)(1) − (2)(3) = −2Apply formula
A⁻¹ = (1/det) × [[d, −b], [−c, a]]Plug in
= (1/−2) × [[1, −2], [−3, 4]]Compute
= [[−1/2, 1], [3/2, −2]]Inverse exists only if determinant is nonzero.
Example 3, Singular matrix (no inverse)
Inverse of [[2, 4], [1, 2]]
Determinant
det = (2)(2) − (4)(1) = 4 − 4 = 0Conclusion
Singular matrix, inverse undefinedDeterminant is zero, rows are linearly dependent.
Example 4, Matrix multiplication
[[1, 2], [3, 4]] × [[5, 6], [7, 8]]
Top-left entry
(1)(5) + (2)(7) = 5 + 14 = 19Top-right entry
(1)(6) + (2)(8) = 6 + 16 = 22Bottom-left entry
(3)(5) + (4)(7) = 15 + 28 = 43Bottom-right entry
(3)(6) + (4)(8) = 18 + 32 = 50Row of left × column of right for each entry. Order matters: AB ≠ BA in general.
Example 5, Transpose
Transpose of [[1, 2], [3, 4]]
Swap rows and columns
Entry (i, j) → (j, i)Result
[[1, 3], [2, 4]]Rows become columns and vice versa.
Matrices are everywhere in math, physics, computer graphics, machine learning, and engineering. This 2×2 matrix calculator handles determinants, inverses, addition, multiplication, and transposes, each with the work shown so you can follow the logic and apply it by hand on exams.
The determinant of [[a, b], [c, d]] is ad − bc. It's a single number that tells you a lot: zero means the matrix is singular (no inverse), positive means the linear transformation preserves orientation, negative means it flips orientation. The absolute value gives the area scaling factor.
The inverse of [[a, b], [c, d]] exists only when det ≠ 0. The formula is (1/det) × [[d, −b], [−c, a]], swap the diagonal entries, negate the off-diagonals, then divide by the determinant. Multiplying a matrix by its inverse gives the identity matrix.
To multiply two 2×2 matrices, take row 1 of the first dot product with column 1 of the second for the (1,1) entry, row 1 dot column 2 for the (1,2) entry, and so on. Each entry of the result requires four multiplications and one addition. Matrix multiplication represents the composition of linear transformations.
The transpose flips a matrix over its diagonal. For [[a, b], [c, d]], the transpose is [[a, c], [b, d]]. Transposes are useful in inner products, symmetric matrices (where A = Aᵀ), and many algorithms in numerical linear algebra. For larger matrices, the same rule applies: row i becomes column i.
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