\( \DeclareMathOperator{\abs}{abs} \newcommand{\ensuremath}[1]{\mbox{$#1$}} \)
| (%i1) | if get ( ' cartan , ' version ) = false then load ( cartan ) $ |
| (%i2) | init_cartan ( [ x1 , x2 , x3 ] ) ; |
\[\operatorname{ }\left[ \ensuremath{\mathrm{dx1}}\operatorname{,}\ensuremath{\mathrm{dx2}}\operatorname{,}\ensuremath{\mathrm{dx3}}\right] \]
| (%i3) | ω : 4 · x1 · x2 · dx1 + 4 · ( x2 ^ 2 ) · dx2 ; |
\[\operatorname{(\omega ) }4 {{\ensuremath{\mathrm{x2}}}^{2}} \ensuremath{\mathrm{dx2}}+4 \ensuremath{\mathrm{x1}}\, \ensuremath{\mathrm{x2}}\, \ensuremath{\mathrm{dx1}}\]
| (%i4) | dω : ext_diff ( ω ) ; |
\[\operatorname{(d\omega ) }-4 \ensuremath{\mathrm{x1}}\, \ensuremath{\mathrm{dx1}}\, \ensuremath{\mathrm{dx2}}\]
| (%i5) | dω ~ ω ; |
\[\operatorname{ }0\]
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