Mathematica [mathematica]- problem with the output

[sandoko]

Hi everyone, i have a problem with mathematica. I am supposed to compute the eigenvalue of a matrix, and I need the expression for the eigenvalues analytically. But it output strange symbols. and I am unable to decipher what it means.

What I got is an output consisting of words like root and the symbol #. Can you guys explain to me why this happen. is there a way for me to obtain the analytical form all the time?

 

[Bill Simpson]

In Mathematica, when a polynomial is complicated enough it will sometimes return Root[p,n] for the n'th root of p[x] instead of the usually numbingly complicated root itself.

Rarely it is possible for Mathematica to find the actual root in that case.

Fortunately in your example if you evaluate
ToRadicals[Eigenvalues[A]]
you will find that it will give you the explicit form of the 3 complicated roots, the last root is zero.

Unfortunately I doubt you are going to be any happier with the 6.5 screenfulls at normal magnification that it takes to show the 3 complicated roots in explicit form. But now you have the analytical form for this particular problem.

 

[sandoko]

oh, thanks for the the explanation especially the ToRadical command.. That's what I need. thanks!