Simplifying Matrix Product

• To: mathgroup at smc.vnet.net
• Subject: [mg20695] Simplifying Matrix Product
• Date: Sun, 7 Nov 1999 02:10:22 -0500
• Organization: California Institute of Technology, Pasadena
• Sender: owner-wri-mathgroup at wolfram.com

```I'm having a little trouble simplifying a product of two matrices on
Mathematica 3.0 for Solaris and Linux. My two matrices are

DERR = {{-(psidot*Cos[psi]*Sin[gamma]) +
psidot*Cos[gamma]*Cos[phi]*Sin[psi],
phidot*Cos[psi]*Sin[phi]) + psidot*Cos[gamma]*Cos[phi]*Sin[psi] +
psidot*Sin[gamma]*Sin[psi],
phidot*Cos[psi]*Sin[phi]) - psidot*Cos[gamma]*Cos[phi]*Sin[psi] -
psidot*Sin[gamma]*Sin[psi]),
psidot*Cos[gamma]*Sin[psi] +
phidot*Sin[phi]*(phidot*Cos[phi]*Sin[gamma] +

INVR = {{Cos[gamma]*Cos[phi]*Cos[psi] - Sin[gamma]*Sin[psi],
Cos[psi]*Sin[gamma] + Cos[gamma]*Cos[phi]*Sin[psi],
-(Cos[gamma]*Sin[phi])}, {-(Cos[phi]*Cos[psi]*Sin[gamma]) -
Cos[gamma]*Sin[psi], Cos[gamma]*Cos[psi] -
Cos[phi]*Sin[gamma]*Sin[psi], Sin[gamma]*Sin[phi]},
{Cos[psi]*Sin[phi], Sin[phi]*Sin[psi], Cos[phi]}}

I type in the following...

FullSimplify[ DERR . INVR ]

...and the UltraSPARC-60 has been chugging for about 12 hours now. Any
ideas??

Cheers,
Phil

```

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