Đẳng thức nào sau đây là đúng?

\(\sin \left( {\alpha + \beta } \right) = \sin \alpha .\sin \beta + {\rm{cos}}\alpha .{\rm{cos}}\beta \).

\({\rm{sin}}\left( {\alpha + \beta } \right) = \sin \alpha .{\rm{cos}}\beta + {\rm{cos}}\alpha {\rm{.sin}}\beta \).

\({\rm{sin}}\left( {\alpha + \beta } \right) = \sin \alpha .{\rm{cos}}\beta - {\rm{cos}}\alpha .{\rm{sin}}\beta \).

\({\rm{sin}}\left( {\alpha + \beta } \right) = {\rm{cos}}\alpha .{\rm{sin}}\beta - \sin \alpha .{\rm{cos}}\beta \).