Identity matrix, 162, 175

Identity principle:

• for polynomials, 260

• for power series, 609

Imaginary eigenvalues, 411

Implicit solution, 34

Improper integral, 401, 558

Improper node, 401, 506

Improved Euler method, 119, 120

• algorithm, 119

• error in, 120

• for systems, 455

Independence: see Linear independence

Independent variable missing, 69

Indicial equation, 632

Indoor temperature oscillations, 56

Infinite-dimensional vector space, 237

Initial condition, 3, 7

Initial position, 12

Initial value problem, 7, 268, 280, 381

• and elementary row operations, 380

• Laplace transform solution, 568

• order n, 280

Initial vector, 356

Initial velocity, 12

Inner product, 250

Integrating factor, 46

Integration of transforms, 591

Interpolating polynomial, 204

Intersection of subspaces, 228

Inverse Laplace transform, 561

• uniqueness of, 565

Inverse matrix, 177

• adjoint formula, 199, 676

• algebra, 178

• algorithm, 181

• solution of linear system, 179

• uniqueness, 177

Inverse of $2\times 2$ matrix, 178

Inverse-square law of gravitation, 99, 373

Invertible matrix, 177

• and determinants, 196

• and row operations, 181

Irregular singular point, 629

Isolated critical point, 514