Question Number 63900 by Rio Michael last updated on 10/Jul/19
Commented by Rio Michael last updated on 10/Jul/19
$${Inthe}\:{Diagram}\:{above}\:{ABCD}\:{and}\:{CDEF}\:{are}\:{parrallelograms} \\ $$$${which}\:{lie}\:{in}\:{thesame}\:{plane}. \\ $$$${A}\overset{\rightarrow} {{B}}=\boldsymbol{{p}}\:,\:{B}\overset{\rightarrow} {{C}}=\boldsymbol{{q}}\:\:{and}\:{C}\overset{\rightarrow} {{F}}=\boldsymbol{{r}}\:\: \\ $$$${by}\:{considering}\:{area}\:{show}\:{that}\:\:\mid\boldsymbol{{p}}×\left(\boldsymbol{{q}}+\boldsymbol{{r}}\right)\mid\:=\:\mid\boldsymbol{{p}}×\boldsymbol{{q}}\mid\:+\:\mid\boldsymbol{{p}}×\boldsymbol{{r}}\mid \\ $$