По определению логарифма х=(4)^-3=1/(4*4*4);
х=1/64
4х+5(3-2х)=5-11х
4х+15-10х=5-11х
4х-10х+11х=5-15
5х=-10
х=-2
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
Tga+ctga=sina/cosa+cosa/sina=(sina^2+cosa^2)/sinacosa=1/sinacosa=a
sinacosa=1/a