Which calculation you need

Matrices and vectors is the general workbench: sums, products, transposes and dot products between two matrices you can keep open side by side. The determinant is the number that says whether a square matrix is invertible: if it is zero the matrix is singular, and the calculator also shows the rank and the inverse where one exists. The linear systems calculator applies the Rouché-Capelli theorem, comparing the rank of the coefficient matrix with that of the augmented one, and separates the three possible cases: a unique solution, infinitely many, or none at all. Eigenvalues and eigenvectors close the loop: they are the directions the matrix merely stretches, and they underpin diagonalisation, principal component analysis and stability analysis.