[latex]8x^3-6x-1=0 [/latex]

сделаем замену  [latex]x=cosx\\ 8cos^3x-6cosx-1=0\\ cosx(8cos^2x-6cosx)-1=0\\ 2cos3x-1=0\\ 2cos3x=1\\ x=\frac{\pi}{9}\\ x=cos(\frac{\pi}{9}})=0.939\\ vtoroy\ koren' posle \ delenia \ nawego \ vyrazhenia \ na \ cos(\frac{\pi}{9}})\\ [/latex]\\ teper'\\ zamena \\ na \\ x=sinx\\ [latex]teper'\\ zamena \\ na \\ x=sinx\\ [/latex] 8sin^3x-6sinx-1=0 -2sin3x-1=0 x=-pi/18+pi*k/2 sin(-pi/18)=-0.17... sin(-5pi/18)=-0.766....