E-CodeEigenvalues and eigenvectors (2×2, 3×3) — a TI-84 Plus CE program
EIGEN is a TI-BASIC program for the TI-84 Plus CE. Every eigenvalue of a 2×2 or 3×3 matrix, complex ones included, from the characteristic polynomial, with the trace and determinant, then a unit eigenvector for each real eigenvalue.
What it asks for and what it shows
It asks for 3 values at its prompts. In the example below it shows TRACE, DET, LAMBDA, V1, V2.
Example run
One of its oracle test cases: “2x2 real: 5 and 2”. The inputs are typed in order, and the results are the values the case expects on the screen.
| Step | Value |
|---|---|
| You enter | |
| Input 1 | 2 |
| Input 2 | {4,1} |
| Input 3 | {2,3} |
| The screen shows | |
TRACE= | 7 |
DET= | 10 |
LAMBDA= | 5 |
V1= | 0.7071067812 |
V2= | 0.7071067812 |
How it's checked
6 test cases, each checked against an independent method. Replayed key by key on a virtual TI-84 Plus CE, they make 43 checks.
How E-Code checks every program
Run it or put it on your calculator
- Open the library in the TI-84 Plus CE calculator and pick “Eigenvalues and eigenvectors (2×2, 3×3)” (EIGEN).
- Put it on your own calculator with a computer and a USB cable, or type it in by hand.
Related programs
- Matrix toolkit: det, inverse, product, power, transpose
- Linear system solver (n equations)
- LU decomposition with partial pivoting
- Vectors: dot, cross, angle, projection
- Quadratic formula solver
All TI-84 Plus CE math programs · All TI-84 Plus CE programs