Cho 2 vec tơ \(\overrightarrow a = \left( {{a_1};{a_2}} \right),\;\overrightarrow b  = \left( {{b_1};{b_2}} \right)\), tìm biểu thức sai:

\(\left( {\overrightarrow {AB}  + \overrightarrow {AC} } \right).\overrightarrow {BC}  = {a^2}\).

\(\overrightarrow {CB} .\overrightarrow {CK}  = \dfrac{{{a^2}}}{8}\).

\(\overrightarrow {AB} .\overrightarrow {AC}  = \dfrac{{{a^2}}}{2}\).

\(\overrightarrow {CB} .\overrightarrow {CK}  = \dfrac{{{a^2}}}{2}\).

$30$

\(20\sqrt 2 \)

\(10\sqrt 3 \)

$20$

${45^{\rm{o}}}$.

${\rm{6}}{{\rm{0}}^{\rm{o}}}$.

${\rm{3}}{{\rm{0}}^{\rm{o}}}$.

${\rm{13}}{{\rm{5}}^{\rm{o}}}$.

\(\overrightarrow a .\overrightarrow b  = \left| {\overrightarrow a } \right|.\left| {\overrightarrow b } \right|\).

\(\overrightarrow a .\overrightarrow b  = 0\).

\(\overrightarrow a .\overrightarrow b  =  - 1\).

\(\overrightarrow a .\overrightarrow b =  - \left| {\overrightarrow a } \right|.\left| {\overrightarrow b } \right|\).

\(\overrightarrow {BA} .\overrightarrow {BC}  = {b^2}.\)

\(\overrightarrow {BA} .\overrightarrow {BC}  = {c^2}.\)

\(\overrightarrow {BA} .\overrightarrow {BC}  = {b^2} + {c^2}.\)

\(\overrightarrow {BA} .\overrightarrow {BC}  = {b^2} - {c^2}.\)  

$2S$

$3S$

$4S$   

$6S$