Cho hình chữ nhật ABCD có AB = 4 cm, AD = 3 cm. Tính \(\left| {\overrightarrow {BC} + \overrightarrow {BA} } \right|\).

A. \(\overrightarrow u = \left( {2; - 1} \right)\);

B. \(\overrightarrow u = \left( { - 2;1} \right)\);  

C. \(\overrightarrow u = \left( {2;1} \right)\);

D. \(\overrightarrow u = \left( { - 2; - 1} \right)\).

A. \(\overrightarrow a .\overrightarrow b = \left| {\overrightarrow a } \right|.\left| {\overrightarrow b } \right|.\sin \left( {\overrightarrow a ,\overrightarrow b } \right)\);

B. \(\overrightarrow a .\overrightarrow b = \left| {\overrightarrow a } \right|.\left| {\overrightarrow b } \right|.\cos \left( {\overrightarrow a ,\overrightarrow b } \right)\);

C. \(\overrightarrow a .\overrightarrow b = - \left| {\overrightarrow a } \right|.\left| {\overrightarrow b } \right|.\cos \left( {\overrightarrow a ,\overrightarrow b } \right)\);                                            

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

A. \(\overrightarrow {MB} = 3\overrightarrow {MA} \);               

B. \(\overrightarrow {MB} = \frac{1}{3}\overrightarrow {AB} \); 

C. \(\overrightarrow {AB} = 4\overrightarrow {MA} \);                

D. \(\overrightarrow {MB} = - 3\overrightarrow {MA} \).

A. sin (180° – α) = – sin α;

B. cos (180° – α) = – cos α;

C. tan (180° – α) = tan α;

D. cot (180° – α) = cot α.