Question

sin15°-sin105°=
sin15°+sin105°=
cos105°+cos75°=
cos75°-cos75°=
Надо превратить на умножение

Answer 1

Решение:

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°