Mệnh đề nào sau đây là đúng?

$0$.

$1$

$2$

$-1$

$\cot (\dfrac{\pi }{2} - \alpha ) = \tan (\alpha )$

$\cot ( - \alpha ) =  - \cot (\alpha )$

$\cot (\pi  + \alpha ) =  - \cot (\alpha )$

$\cot (\pi  - \alpha ) =  - \cot (\alpha )$

$ - 3 - \sqrt 3 $.

$2 - 3\sqrt 3 $.

$\dfrac{{2\sqrt 3 }}{{\sqrt 3  - 1}}\,$.

$\dfrac{{1 - \sqrt 3 }}{{\sqrt 3 }}\,$.

$\sin \left( {{{180}^0}-a} \right) = -\cos a$.

$\sin \left( {{{180}^0}-a} \right) =  - \sin a$.

$\sin \left( {{{180}^0}-a} \right) = \sin a$.

$\sin \left( {{{180}^0}-a} \right) = \cos a$.

$\tan (\pi  + \alpha ) =  - \tan (\alpha )$

$\tan ( - \alpha ) =  - \tan (\alpha )$

$\tan (\dfrac{\pi }{2} - \alpha ) = \cot (\alpha )$

$\tan (\pi  - \alpha ) =  - \tan (\alpha )$

$\dfrac{7}{4}$

$\dfrac{1}{4}$

\(7\)

$\dfrac{{13}}{4}$