CS223 · Annotated SlidesChapter 5 — Diagonalization
Chapter 5 · Annotated slides

Diagonalization

A = PDP⁻¹ and fast powers Aᵏ = PDᵏP⁻¹, the Diagonalization Theorem (n independent eigenvectors), the step-by-step procedure, and when distinct eigenvalues guarantee diagonalizability.

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  1. A is diagonalizable ⇔ it has n linearly independent eigenvectors. Then A = PDP⁻¹: P’s columns are eigenvectors, D’s diagonal the matching eigenvalues. Aᵏ = PDᵏP⁻¹.
Memory trickn distinct eigenvalues ⇒ diagonalizable (sufficient, not necessary).
🎯 How this can come up · 2 questions
True / False

A 3×3 matrix with 3 distinct eigenvalues is diagonalizable.

True / False

Every diagonalizable matrix is invertible.

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        1. Steps: eigenvalues → basis of each eigenspace → if the total is n vectors, build P and D (same order).
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