Hệ thức nào sau đây là sai?
A.\({\rm{cos5}}\alpha {\rm{.cos2}}\alpha = \frac{1}{2}\left( {{\rm{cos}}7\alpha + {\rm{cos}}3\alpha } \right).\)
B.\(\sin 5\alpha \cos 2\alpha = \frac{1}{2}\left( {\sin 3\alpha + \sin 7\alpha } \right).\)
C.\({\rm{sin6}}\alpha .\sin 2\alpha = \frac{1}{2}\left( {\cos 4\alpha - \cos 8\alpha } \right).\)
D.\({\rm{cos2}}\alpha {\rm{.sin5}}\alpha = \frac{1}{2}\left( {\sin 7\alpha - \sin 3\alpha } \right).\)
A.\({\rm{cos5}}\alpha {\rm{.cos2}}\alpha = \frac{1}{2}\left( {{\rm{cos}}7\alpha + {\rm{cos}}3\alpha } \right).\)
B.\(\sin 5\alpha \cos 2\alpha = \frac{1}{2}\left( {\sin 3\alpha + \sin 7\alpha } \right).\)
C.\({\rm{sin6}}\alpha .\sin 2\alpha = \frac{1}{2}\left( {\cos 4\alpha - \cos 8\alpha } \right).\)
D.\({\rm{cos2}}\alpha {\rm{.sin5}}\alpha = \frac{1}{2}\left( {\sin 7\alpha - \sin 3\alpha } \right).\)
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Hóa Học lớp 12
