FormelSkalarprodukt in 3d (Definition) $$ \boldsymbol{a} ~\cdot~ \boldsymbol{b} ~=~ a_1b_1 ~+~ a_2b_2 ~+~ a_3b_3 $$
FormelDoppeltes Kreuzprodukt (BAC-CAB-Regel) $$ \boldsymbol{a} ~\times~ \left( \boldsymbol{b} ~\times~ \boldsymbol{c} \right) ~=~ \boldsymbol{b} \left( \boldsymbol{a} ~\cdot~ \boldsymbol{c} \right) ~-~ \boldsymbol{c} \left( \boldsymbol{a} ~\cdot~ \boldsymbol{b} \right) $$