A.\(\sin \dfrac{{A + C}}{2} = \cos \dfrac{B}{2}\)
B.\(\cos \dfrac{{A + C}}{2} = \sin \dfrac{B}{2}\)
C.\(\sin \left( {A + B} \right) = \sin C\)
D.\(\cos \left( {A + B} \right) = \cos C\)

A.\(\sin C =  - \,\sin \left( {A + B} \right)\)
B.\(\cos C = \cos \left( {A + B} \right)\)
C.\(\tan C = \tan \left( {A + B} \right)\)
D.\(\cot C =  - \,\cot \left( {A + B} \right)\)

A.\(\sin \left( {A + C} \right) =  - \sin B\)
B.\(\cos \left( {A + C} \right) =  - \cos B\)
C.\(\tan \left( {A + C} \right) = \tan B\)
D.\(\cot \left( {A + C} \right) = \cot B\)

A.\(\sin \left( {A + B} \right) = \cos C\)
B.\(\cos A = \sin B\)
C.\(\tan A = \cot \left( {B + \dfrac{\pi }{2}} \right)\)
D.\(\cos \dfrac{{A + B}}{2} = \sin \dfrac{C}{2}\)

A.\(\sin \left( {\dfrac{{A + B}}{2}} \right) = \cos \dfrac{C}{2}\)
B.\(\sin \left( {\dfrac{{A + B}}{2}} \right) =  - \cos \dfrac{C}{2}\)
C.\(\sin \left( {\dfrac{{A + B}}{2}} \right) = \sin \dfrac{C}{2}\)
D.\(\sin \left( {\dfrac{{A + B}}{2}} \right) =  - \sin \dfrac{C}{2}\)

A.\(M =  - \cos A\)
B.\(M = \cos A\)
C.\(M = \sin A\)
D.\(M =  - \sin A\)

A.\(\sin \left( {A + B} \right) =  - \sin C\)
B.\(\sin \left( {\dfrac{{A + B}}{2}} \right) = \cos \dfrac{C}{2}\)
C.\(\cos \left( {A + B} \right) = \cos C\)
D.\(\tan \left( {A + B} \right) = \tan C\)

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.\(1\)
B.\(2\)
C.\(3\)
D.\(4\)

A.\(\Delta ABC\) cân tại \(C\)
B.\(\Delta ABC\) vuông tại \(B\)
C.\(\Delta ABC\) vuông tại \(C\)
D.\(\Delta ABC\) cân tại \(B\)