4 sin25 sin35 sin85Как лучше преобразовать? 

 [latex]4sin25*sin35*sin85 = \\\\ sin25*sin35*sin85=\frac{cos10-cos60}{2}*sin85=\frac{cos10-0.5}{2}*sin85 =\\\\ \frac{cos10-0.5}{2}*cos5 = (\frac{cos10}{2}-\frac{1}{4})*cos5=\\\\ (cos^25-\frac{1}{2}-\frac{1}{4})*cos5 = (cos^25-\frac{3}{4})*cos5=\frac{cos15}{4}\\\\ 4*\frac{cos15}{4}=cos15[/latex]  Ответ [latex]cos15[/latex]