Question

ctg(-п/4) sin13п/6 cos(-2п/3)

Answer 1

$ctg(-pi/4)sin(13pi/6)cos(-2pi/3)=\\=-ctg(pi/4)*sin(2pi+pi/6)cos(2pi/3)=\\=-1*sin(pi/6)*(-1/2)=1/2*1/2=1/4$