Sin(60°+a)sin(60°-a) = (1/2)*[cos(60° + α - 60° + α<span>) -
- cos(</span>60° + α + 60° - α)] = (1/2)*[cos2α - cos(120°)] =
<span>= (1/2)*[cos2α + cos(60°)] = (1/2)*[cos2α + 1/2)] = (1/2)*cos2α + 1/4</span>
Решение смотрите во вкладке.
П/3+п/6-п/4=(8п+4п-6п)/24=6п/24=п/4 (45°)
2х+3=x-2
3+2=x-2x
5= -x
-10+3=-5-2