(%i2) load ( basic ) $
if get ( ' cartan , ' version ) = false then load ( cartan ) $
(%i3) init_cartan ( [ x1 , x2 , x3 ] ) ;

\[\operatorname{ }\left[ \ensuremath{\mathrm{dx1}}\operatorname{,}\ensuremath{\mathrm{dx2}}\operatorname{,}\ensuremath{\mathrm{dx3}}\right] \]

1-Formen ω, η, σ
(%i6) ω : ω1 · dx1 + ω2 · dx2 + ω3 · dx3 ;
η : η1 · dx1 + η2 · dx2 + η3 · dx3 ;
σ : σ1 · dx1 + σ2 · dx2 + σ3 · dx3 ;

\[\operatorname{(\omega ) }\ensuremath{\mathrm{dx3}}\, \ensuremath{\mathrm{\omega 3}}+\ensuremath{\mathrm{dx2}}\, \ensuremath{\mathrm{\omega 2}}+\ensuremath{\mathrm{dx1}}\, \ensuremath{\mathrm{\omega 1}}\]

\[\operatorname{(\eta ) }\ensuremath{\mathrm{dx3}}\, \ensuremath{\mathrm{\eta 3}}+\ensuremath{\mathrm{dx2}}\, \ensuremath{\mathrm{\eta 2}}+\ensuremath{\mathrm{dx1}}\, \ensuremath{\mathrm{\eta 1}}\]

\[\operatorname{(\sigma ) }\ensuremath{\mathrm{dx3}}\, \ensuremath{\mathrm{\sigma 3}}+\ensuremath{\mathrm{dx2}}\, \ensuremath{\mathrm{\sigma 2}}+\ensuremath{\mathrm{dx1}}\, \ensuremath{\mathrm{\sigma 1}}\]

Äußeres Produkt von ω und η
(%i7) facsum ( ω ~ η , dx1 , dx2 , dx3 ) ;

\[\operatorname{ }-\ensuremath{\mathrm{dx2}}\, \ensuremath{\mathrm{dx3}}\, \left( \ensuremath{\mathrm{\eta 2}}\, \ensuremath{\mathrm{\omega 3}}-\ensuremath{\mathrm{\eta 3}}\, \ensuremath{\mathrm{\omega 2}}\right) -\ensuremath{\mathrm{dx1}}\, \ensuremath{\mathrm{dx3}}\, \left( \ensuremath{\mathrm{\eta 1}}\, \ensuremath{\mathrm{\omega 3}}-\ensuremath{\mathrm{\eta 3}}\, \ensuremath{\mathrm{\omega 1}}\right) -\ensuremath{\mathrm{dx1}}\, \ensuremath{\mathrm{dx2}}\, \left( \ensuremath{\mathrm{\eta 1}}\, \ensuremath{\mathrm{\omega 2}}-\ensuremath{\mathrm{\eta 2}}\, \ensuremath{\mathrm{\omega 1}}\right) \]

Äußeres Produkt von ω, η, σ
(%i8) factor ( ω ~ η ~ σ ) ;

\[\operatorname{ }\ensuremath{\mathrm{dx1}}\, \ensuremath{\mathrm{dx2}}\, \ensuremath{\mathrm{dx3}}\, \left( \ensuremath{\mathrm{\eta 1}}\, \ensuremath{\mathrm{\sigma 2}}\, \ensuremath{\mathrm{\omega 3}}-\ensuremath{\mathrm{\eta 2}}\, \ensuremath{\mathrm{\sigma 1}}\, \ensuremath{\mathrm{\omega 3}}-\ensuremath{\mathrm{\eta 1}}\, \ensuremath{\mathrm{\sigma 3}}\, \ensuremath{\mathrm{\omega 2}}+\ensuremath{\mathrm{\eta 3}}\, \ensuremath{\mathrm{\sigma 1}}\, \ensuremath{\mathrm{\omega 2}}+\ensuremath{\mathrm{\eta 2}}\, \ensuremath{\mathrm{\sigma 3}}\, \ensuremath{\mathrm{\omega 1}}-\ensuremath{\mathrm{\eta 3}}\, \ensuremath{\mathrm{\sigma 2}}\, \ensuremath{\mathrm{\omega 1}}\right) \]


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