Объяснение:
Sin108° =sin(90° +18°)=cos18°
sin210°=sin(180° +30°)=-sin30°=-1/2
сos 12° Sin108° − sin18°Sin12° +sin 210°=сos 12°cos18° − sin18°Sin12° +sin210°=
=cos(12°+18°)-(1/2)=cos(30°)-(1/2)=((√3)/2)-(1/2)
