5sin11p/12*cos11p/12
5sin11p/12*cos11p/12=2,5 * 2 * sin11p/12*cos11p/12 = 2,5 * sin(2*11p/12) = 2,5 * sin(11p/6) = 2,5 * sin(-p/6) = 2,5 * (-0,5) = -1,25