Sin(-385°)*sin(555°)-sin(-295°)*sin(165°)-cos(-1050°)=

= -Sin385°*Sin555° +Sin295°*Sin165°-Cos1050°=
= -Sin(360°+25°)*Sin(540°+15°)+Sin(270°+25°)*Sin(180°-15°) - Cos(1080° - 30°)=
= Sin25°*Sin15° -Sin25°*Sin15° - Cos30°= -Cos30°= -