三焦点テンソル
l ′ t ( ∑ i x i T i ) l ′′ = 0 {\displaystyle {\mathbf {l} }^{\prime t}\left(\sum _{i}x_{i}{\mathbf {T} }_{i}\right){\mathbf {l} }''=0}
l ′ t ( ∑ i x i T i ) [ x ′′ ] × = 0 t {\displaystyle {\mathbf {l} }^{\prime t}\left(\sum _{i}x_{i}{\mathbf {T} }_{i}\right)[{\mathbf {x} }'']_{\times }={\mathbf {0} }^{t}}
[ x ′ ] × ( ∑ i x i T i ) l ′′ = 0 {\displaystyle [{\mathbf {x} }']_{\times }\left(\sum _{i}x_{i}{\mathbf {T} }_{i}\right){\mathbf {l} }''={\mathbf {0} }}
[ x ′ ] × ( ∑ i x i T i ) [ x ′′ ] × = 0 3 × 3 {\displaystyle [{\mathbf {x} }']_{\times }\left(\sum _{i}x_{i}{\mathbf {T} }_{i}\right)[{\mathbf {x} }'']_{\times }={\mathbf {0} }_{3\times 3}}
ここで [ ⋅ ] × {\displaystyle [\cdot ]_{\times }} は、交代外積行列を意味する。