1.
sin15°- sin105° = 2cos(0.5(15° + 105°))· sin 0.5(15° - 105°) =
= - 2 cos 60° · sin 45°
2.
sin15°+ sin105° = 2sin(0.5(15° + 105°))· cos 0.5(15° - 105°) =
= 2 sin 60° · cos 45°
3.
cos105° + cos75° = 2cos (0.5(105° + 75°)) · cos (0.5(105° - 75°)) =
= 2 cos 90° · cos 15°
4.
cos75° - cos105° = -2 sin(0.5(75° + 105°)) · sin (0.5(75° - 105°)) =
= 2 sin 90° · sin15°
1.
sin15°- sin105° = 2cos(0.5(15° + 105°))· sin 0.5(15° - 105°) =
= - 2 cos 60° · sin 45°
2.
sin15°+ sin105° = 2sin(0.5(15° + 105°))· cos 0.5(15° - 105°) =
= 2 sin 60° · cos 45°
3.
cos105° + cos75° = 2cos (0.5(105° + 75°)) · cos (0.5(105° - 75°)) =
= 2 cos 90° · cos 15°
4.
cos75° - cos105° = -2 sin(0.5(75° + 105°)) · sin (0.5(75° - 105°)) =
= 2 sin 90° · sin15°