Help with Root function
- To: mathgroup at smc.vnet.net
- Subject: [mg79407] Help with Root function
- From: jeremito <jeremit0 at gmail.com>
- Date: Thu, 26 Jul 2007 05:28:38 -0400 (EDT)
I am trying to find the eigenvalues of a 3x3 matrix with non-numeric elements. This requires finding the roots of cubic polynomials. Mathematica can do this, but I know how to interpret its output. For example In[1]:= B = {{a, 1, 1}, {1, b, 1}, {1, 1, c}} Out[1]= {{a, 1, 1}, {1, b, 1}, {1, 1, c}} In[2]:= Eigenvalues[B] Out[2]= {Root[-2 + a + b + c - a b c + (-3 + a b + a c + b c) #1 + (-a - b - c) #1^2 + #1^3 &, 1], Root[-2 + a + b + c - a b c + (-3 + a b + a c + b c) #1 + (-a - b - c) #1^2 + #1^3 &, 2], Root[-2 + a + b + c - a b c + (-3 + a b + a c + b c) #1 + (-a - b - c) #1^2 + #1^3 &, 3]} How can I get Mathematica to give me the full answer? I know it is long and ugly, but at least I can do something with it. I can't do anything with what it gives me now. Does that make sense? Thanks, Jeremy