A.\(\cos \alpha  + \sin \alpha  < 0\) và \(\sin 2\alpha  < 0\)
B.\(\cos \alpha  + \sin \alpha  > 0\) và \(\cos 2\alpha  < 0\)
C.\(\cos \alpha  - \sin \alpha  > 0\) và \(\sin 2\alpha  < 0\)
D.\(\cos \alpha  - \sin \alpha  > 0\) và \(\cos 2\alpha  < 0\)

A.\({\rm{I}}\)
B.\({\mathop{\rm II}\nolimits} \)
C.\({\mathop{\rm III}\nolimits} \)
D.\({\rm{IV}}\)

A.\(\dfrac{{\sqrt 3 }}{2}\)
B.\(\dfrac{1}{2}\)
C.\(\dfrac{{\sqrt 2 }}{2}\)
D.\( - \dfrac{1}{2}\)

A.\(\sqrt 3 \)
B.\( - \sqrt 3 \)
C.\(\dfrac{{\sqrt 3 }}{2}\)
D.\( - \dfrac{{\sqrt 3 }}{2}\)

A.\(\cos {150^0} = \dfrac{{\sqrt 3 }}{2}\)
B.\(\cot {150^0} = \sqrt 3 \)
C.\(\tan {150^0} =  - \dfrac{1}{{\sqrt 3 }}\)
D.\(\sin {150^0} =  - \dfrac{{\sqrt 3 }}{2}\)

A.\(\dfrac{7}{{16}}\)
B.\(\dfrac{{\sqrt 7 }}{4}\)
C.\( - \dfrac{{\sqrt 7 }}{4}\)
D.\( - \dfrac{7}{{16}}\)

A.\(\sin A.\sin B.\sin C < 0\)
B.\(\cos \,\dfrac{A}{2} \cdot \cos \,\dfrac{B}{2} \cdot \cos \,\dfrac{C}{2} > 0\)
C.\(\tan \,\dfrac{A}{2} + \tan \,\dfrac{B}{2} + \tan \,\dfrac{C}{2} > 0\)
D.\(\sin A + \sin B + \sin C > 0\)

A.\(\dfrac{5}{{\sqrt {13} }}\)
B.\( - \dfrac{5}{{\sqrt {13} }}\)
C.\( - \dfrac{5}{{13}}\)
D.\(\dfrac{5}{{13}}\)

A.\(\cos \alpha  = \dfrac{2}{3}\)
B.\(\cos \alpha  =  - \dfrac{2}{3}\)
C.\(\cos \alpha  = \dfrac{{2\sqrt 2 }}{3}\)
D.\(\cos \alpha  =  - \dfrac{{2\sqrt 2 }}{3}\)

A.\(\sin \left( {\alpha  + \beta } \right) =  - \dfrac{{2 + 2\sqrt {10} }}{9}\)
B.\(\sin \left( {\alpha  + \beta } \right) = \dfrac{{2\sqrt {10}  - 2}}{9}\)
C.\(\sin \left( {\alpha  + \beta } \right) = \dfrac{{\sqrt 5  - 4\sqrt 2 }}{9}\)
D.\(\sin \left( {\alpha  + \beta } \right) = \dfrac{{\sqrt 5  + 4\sqrt 2 }}{9}\)