1) sin 780° =
2) cos (13/6) =
Пошаговое объяснение:
1) sin 780° = sin (720° + 60°) = sin (2 * 360° + 60°) = sin (60°) =
2) cos (13/6) = cos (2 + /6) = cos (/6) = cos (30°) =
/6) = /6) = cos (2 + /6) = cos (/6) = cos (30°) = 
