Actually it is fun, though a bit tedious. My HP-49G+ calculator, or Mathematica or Maple on my laptop, can of course determine Eigenvalues and Eigenvectors automatically, but the point of today’s Linear Algebra class (and Monday’s quiz) is to learn how to do it ourselves.

Computing an matrix of cofactors (and its transpose, the adjoint) is pretty tedious too. It doesn’t appear that the HP 49G+ has a built-in function to do that, so I wrote these during class.

  MINOR:
« UNROT ROW- DROP SWAP COL- DROP DET »

COFACTORS:
« DUP SIZE DUP 1 GET R→I
→ a s n
«  1 n FOR i
1 n FOR j
a i j MINOR
-1 i j + ^ *
NEXT
NEXT
s →ARRY
»
»

ADJOINT:
« COFACTORS TRAN »