> #============================

> # Testaufgabe 3

> #============================

> restart; with(linalg):

Warning, new definition for norm

Warning, new definition for trace

> read ` test_a3.dat`;

> a_save:=evalm(a); read `cholesky.src `;

> ...

> # positiv definit: d_i > 0

> solve(d[3] > 0, alpha);

> solve(d[4] > 0, alpha);

> evalf(sqrt(15));

> # also alpha in (-15/4,15/4)