1) tgx>√3/3
π/6+πn<x<π/2+πn,n∈z
2)ctgx<-1
3π/4+πn<x<π+πn,n∈z
3) cosx≥√2/2
-π/4+2πn≤x≤π/4+2πn,n∈z
4) sinx≤-√3/2
-2π/3+2πn≤x≤-π/3+2πn,n∈z
Решение
<span>cos40 cos20-sin40 sin20 = cos(40 + 20) = cos60 = 1/2</span>
Y ' =(6x-15)e^x + (3x^2-15x+15)e^x=(6x-15+ 3x^2 -15x+15)e^x=(3x^2 -9x)e^x=0. e^x не=0, тогда 3x^2 -9x=0, 3x(x-3)=0, x=0; 3.