A.\(\sin 2A + \sin 2B + \sin 2C = 4\cos A.\cos B.\cos C\)
B.\(\sin 2A + \sin 2B + \sin 2C =  - 4\cos A.\cos B.\cos C\)
C.\(\sin 2A + \sin 2B + \sin 2C = 4\sin A.\sin B.\sin C\)
D.\(\sin 2A + \sin 2B + \sin 2C =  - 4\sin A.\sin B.\sin C\)

A.cân tại \(C\)
B.vuông tại \(B\)
C.cân tại \(A\)
D.đều

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

A.
B.
C.
D.

A.\(172\)
B.\(168\)
C.\(178\)
D.\(180\)

A.\(\dfrac{{\sqrt 6 }}{6}\)
B.\(\dfrac{{\sqrt 2 }}{3}\)
C.\(\dfrac{{\sqrt 2 }}{6}\)
D.\(\dfrac{{\sqrt 3 }}{6}\)

A.\(\dfrac{{a\sqrt {10} }}{{40}}\)
B.\(\dfrac{{8a}}{3}\)
C.\(\dfrac{{3a}}{8}\)
D.\(\dfrac{{3a}}{2}\)

A.\(8\)
B.\(10\)
C.\(\dfrac{{32}}{3}\)
D.\(\dfrac{{28}}{3}\)

A.\(4\)
B.\(8\)
C.\(2\)
D.\(6\)

A.\(7\)
B.\(4\)
C.\(3\)
D.\(6\)