1)y'=2*2sin(3x)*cos(3x)*3
y'=6sin(6x)
y'(-pi/2)=6*sin(-6pi/2)=6*sin(-3pi)=-6*sin(3pi)=0
2)y'=1/ctg^2(4x)*2ctg(4x)*(-1/sin^2(4x))*4= -8/(ctg(4x)*sin^2(4x))
y'(pi/16)=-8/(ctg(4pi/16)*sin^2(4pi/16))=-8/(ctg(pi/4)*sin^2(pi/4))=-8/(1*(1/(2)^(1/2))^2)=-8*2=-16
3)y'=1/(2x)
y'(1/8)=1/(2*1/8)=8/2=4