Trong tam giác $ABC$  có

$25$

$5$     

$6$     

$7$

$2$.

$0$.

$\sqrt 3$.

$1$.

$\dfrac{1}{2}$.

$- \dfrac{1}{2}$.

$\dfrac{{\sqrt 2 }}{2}$.   

$- \dfrac{{\sqrt 2 }}{2}$.

$\overrightarrow a  = \left( {2; - 1} \right)$  và  $\overrightarrow b  = \left( { - 3;4} \right)$.

$\overrightarrow a  = \left( {3; - 4} \right)$  và  $\overrightarrow b  = \left( { - 3;4} \right)$.

$\overrightarrow a  = \left( { - 2; - 3} \right)$  và  $\overrightarrow b  = \left( { - 6;4} \right)$.

$\overrightarrow a  = \left( {7; - 3} \right)$  và  $\overrightarrow b  = \left( {3; - 7} \right)$.

$\cos \alpha  < \cos \beta$.

$\sin \alpha  < \sin \beta$.

$\tan \alpha  + \tan \beta  > 0$.

$\cot \alpha > \cot \beta$.

$10$

$\dfrac{{5\sqrt 6 }}{2}$                  

$5\sqrt 3$      

$5\sqrt 2$

${a^2} = {b^2} + {c^2} - bc\cos A$           

${a^2} = {b^2} + {c^2} + bc\cos A$

${a^2} = {b^2} + {c^2} - 2bc\cos A$          

${a^2} = {b^2} + {c^2} + 2bc\cos A$