У = Cos²x
Δy = Cos²(x + Δx) - Cos²x = (Cos (x + Δx) - Cos x)(Cos(x + Δx) + Cos x)=
=-2Sin(x+Δх/2) SinΔx/2 ·2Cos(x + Δх/2) CosΔx/2
lim( -2Sin(x+Δх/2) SinΔx/2 ·2Cos(x + Δх/2) CosΔx/2)/Δх =
(Δх = Δх·2/2) = - 2 Sin x Cos x
(3-5z)/(2z+1)-1+z=0
z≠-0,5
3-5z-2z-1+2z²+z=0
2z²-6z+2=0
z²-3z+1=0
D=9-4=5
z1=(3-√5)/2
z2=(3+√5)/2
-0.4x-3=5-0.8x
(0.8-0.4)x=3+5
0.4x=8
x=8*0.4
x=3.2
Четыре целых одна шестая.