3sin13пи/12 *cos13п/12
Получаеться: 3/2*2sin(13п/12)*cos(13п/12) 3/2*sin(2*13п/12) 3/2*sin(13п/6) 3/2*1/2 3/4
3sin(13π/12) * cos(13π/12) = 1.5 * (2 * sin(13π/12) * cos(13π/12)) = 1.5 * sin(13π/6) = 1.5 * sin(π/6) = 1.5 * 0.5 = 0.75